Modification of UV absorption profile of polymer film reflectors to increase solar-weighted reflectance

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jorgensen, Gary; Gee, Randall C.; White, David

Provided are reflective thin film constructions including a reduced number of layers, which provides for increased solar-weighted hemispherical reflectance and durability. Reflective films include those comprising an ultraviolet absorbing abrasion resistant coating over a metal layer. Also provided are ultraviolet absorbing abrasion resistant coatings and methods for optimizing the ultraviolet absorption of an abrasion resistant coating. Reflective films disclosed herein are useful for solar reflecting, solar collecting, and solar concentrating applications, such as for the generation of electrical power.

Room-temperature synthesis and photoluminescence of hexagonal CePO4 nanorods

NASA Astrophysics Data System (ADS)

Zhu, J.; Zhang, K.; Zhao, H. Y.

2018-01-01

Hexagonal CePO4 nanorods were synthesized via a simple chemical precipitation route at room-temperature without the presence of surfactants and then characterized by powder X-ray diffraction (XRD), energy-dispersive X-ray (EDX) spectrometry, scanning electron microscopy (SEM), transmission electron microscopy (TEM), ultraviolet-visible (UV-vis) absorption and photoluminescence (PL) spectroscopy. Hexagonal CePO4 nanorods exhibit strong ultraviolet absorption and ultraviolet luminescence, which correspond to the electronic transitions between 4f and 5d state of Ce3+ ions.

Measurement of temperature profiles in flames by emission-absorption spectroscopy

NASA Technical Reports Server (NTRS)

Simmons, F. S.; Arnold, C. B.; Lindquist, G. H.

1972-01-01

An investigation was conducted to explore the use of infrared and ultraviolet emission-absorption spectroscopy for determination of temperature profiles in flames. Spectral radiances and absorptances were measured in the 2.7-micron H2O band and the 3064-A OH band in H2/O2 flames for several temperature profiles which were directly measured by a sodium line-reversal technique. The temperature profiles, determined by inversion of the infrared and ultraviolet spectra, showed an average disagreement with line-reversal measurements of 50 K for the infrared and 200 K for the ultraviolet at a temperature of 2600 K. The reasons for these discrepancies are discussed in some detail.

The ultraviolet interstellar extinction curve in the Pleiades

NASA Technical Reports Server (NTRS)

Witt, A. N.; Bohlin, R. C.; Stecher, T. P.

1981-01-01

The wavelength dependence of ultraviolet extinction in the Pleiades dust clouds has been determined from IUE observations of HD 23512, the brightest heavily reddened member of the Pleiades cluster. There is evidence for an anomalously weak absorption bump at 2200 A, followed by an extinction rise in the far ultraviolet with an essentially normal slope. A relatively weak absorption band at 2200 A and a weak diffuse absorption band at 4430 A seem to be common characteristics of dust present in dense clouds. Evidence is presented which suggests that the extinction characteristics found for HD 23512 are typical for a class of extinction curves observed in several cases in the Galaxy and in the LMC.

MSG-7: Molecular absorption processes related to the penetration of ultraviolet solar radiation into the middle atmosphere

NASA Technical Reports Server (NTRS)

Frederick, J. E.; Blake, A. J.; Freeman, D. E.; Nicholls, R. W.; Ogawa, T.; Simon, P. C.

1983-01-01

The information presently available on the absorption cross sections of O2 and O3 with attention to the application of these data in middle atmospheric science is reviewed. The cross sections values reported by different groups are intercompared in tabular form where feasible, and specific values are recommended when there is a basis for preferring a particular set of results over other available data. When no such basis exists, the differences among published cross sections then serve to indicate a range of uncertainty. In these cases the need for additional work is indicated. Specific topics addressed are the absorption of molecular oxygen at Lyman alpha, in the Schumann-Runge continuum, in the Schumann-Runge bands, and in the Herzberg continuum. For ozone, the Hartley and Huggins bands are considered.

Complex refractive index of Martian dust - Mariner 9 ultraviolet observations

NASA Technical Reports Server (NTRS)

Pang, K.; Ajello, J. M.; Hord, C. W.; Egan, W. G.

1976-01-01

Mariner 9 ultraviolet spectrometer observations of the 1971 dust clouds obscuring the surface of Mars have been analyzed by matching the observed dust phase function with Mie scattering calculations for size distributions of homogeneous and isotropic material. Preliminary results indicate an effective particle radius of not less than 0.2. The real component of the index of refraction is not less than 1.8 at both 268 and 305 nm; corresponding values for the imagery component are 0.02 and 0.01. These values are consistent with those found by Mead (1970) for the visible and near-visible wavelengths. The refractive index and the absorption coefficient increase rapidly with decreasing wavelength in going from the visible to the ultraviolet, indicating the presence of an ultraviolet absorption band which may shield organisms from ultraviolet irradiation.

Contrastive Study on the Structure and the Ultraviolet Absorption Property of Multiple-Doped and Element-Doped ZnO Thin Films

NASA Astrophysics Data System (ADS)

Xu, Yunyun; Zhang, Tao; Lin, Zhenrong; Tian, Yanfeng; Zhou, Shandan

Sb2O3- and CeO2-doped ZnO thin films were prepared by RF magnetron sputtering technique. The influence of Sb2O3 and CeO2 on the structure and ultraviolet (UV) absorption properties was studied by X-ray diffraction and UV-Vis spectrophotometry. Results show that multiple doping of films had a prominent effect on the development of crystal grains and the UV absorption property. Ce and Sb exist in many forms in the ZnO film. The multiple-doped films also show enhanced UVA absorption, and the UV absorption peak widens and the absorption intensity increases. Sb plays a dominant role on the structure and UV absorption of ZnO thin films, which are enhanced by Ce.

MSG-7: molecular absorption processes related to the penetration of ultraviolet solar radiation into the middle atmosphere

DOE Office of Scientific and Technical Information (OSTI.GOV)

Frederick, J.E.; Blake, A.J.; Freeman, D.E.

1983-07-01

The information presently available on the absorption cross sections of O2 and O3 with attention to the application of these data in middle atmospheric science is reviewed. The cross sections values reported by different groups are intercompared in tabular form where feasible, and specific values are recommended when there is a basis for preferring a particular set of results over other available data. When no such basis exists, the differences among published cross sections then serve to indicate a range of uncertainty. In these cases the need for additional work is indicated. Specific topics addressed are the absorption of molecularmore » oxygen at Lyman alpha, in the Schumann-Runge continuum, in the Schumann-Runge bands, and in the Herzberg continuum. For ozone, the Hartley and Huggins bands are considered.« less

Ultraviolet absorption of common spacecraft contaminants. [to control effects of contaminants on optical systems

NASA Technical Reports Server (NTRS)

Colony, J. A.

1979-01-01

Organic contamination of ultraviolet optical systems is discussed. Degradation of signal by reflection, scattering, interference, and absorption is shown. The first three processes depend on the physical state of the contaminant while absorption depends on its chemical structure. The latter phenomenon is isolated from the others by dissolving contaminants in cyclohexane and determining absorption spectra from 2100A to 3600A. A variety of materials representing the types of contaminants responsible for most spaceflight hardware problems is scanned and the spectra is presented. The effect of thickness is demonstrated for the most common contaminant, di(2 ethyl hexyl)phthalate, by scanning successive dilutions.

Picosecond flash spectroscopic studies on ultraviolet stabilizers and stabilized polymers

NASA Technical Reports Server (NTRS)

Scott, G. W.

1982-01-01

Spectroscopic and excited state decay kinetics are reported for monomeric and polymeric forms of ultraviolet stabilizers in the 2-(2'-hydroxyphenyl)-benzotriazole and 2-hydroxybenzophenone classes. For some of these molecules in various solvents at room temperature, (1) ground state absorption spectra, (2) emission spectra, (3) picosecond time-resolved transient absorption spectra, (4) ground state absorption recovery kinetics, (5) emission kinetics, and (6) transient absorption kinetics are reported. In the solid state at low temperatures, emission spectra and their temperature dependent kinetics up to approximately 200K as well as, in one case, the 12K excitation spectra of the observed dual emission are also reported.

Carrier-Specific Femtosecond XUV Transient Absorption of PbI 2 Reveals Ultrafast Nonradiative Recombination

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lin, Ming-Fu; Verkamp, Max A.; Leveillee, Joshua

Femtosecond carrier recombination in PbI 2 is measured using tabletop high-harmonic extreme ultraviolet (XUV) transient absorption spectroscopy and ultrafast electron diffraction. XUV absorption from 45 eV to 62 eV measures transitions from the iodine 4d core level to the conduction band density of states. Photoexcitation at 400 nm creates separate and distinct transient absorption signals for holes and electrons, separated in energy by the 2.4 eV band gap of the semiconductor. The shape of the conduction band and therefore the XUV absorption spectrum is temperature dependent, and nonradiative recombination converts the initial electronic excitation to thermal excitation within picoseconds. Ultrafastmore » electron diffraction (UED) is used to measure the lattice temperature and confirm the recombination mechanism. Lastly, the XUV and UED results support a 2nd-order recombination model with a rate constant of 2.5x10 -9 cm 3/s.« less

Carrier-Specific Femtosecond XUV Transient Absorption of PbI 2 Reveals Ultrafast Nonradiative Recombination

DOE PAGES

Lin, Ming-Fu; Verkamp, Max A.; Leveillee, Joshua; ...

2017-11-30

Femtosecond carrier recombination in PbI 2 is measured using tabletop high-harmonic extreme ultraviolet (XUV) transient absorption spectroscopy and ultrafast electron diffraction. XUV absorption from 45 eV to 62 eV measures transitions from the iodine 4d core level to the conduction band density of states. Photoexcitation at 400 nm creates separate and distinct transient absorption signals for holes and electrons, separated in energy by the 2.4 eV band gap of the semiconductor. The shape of the conduction band and therefore the XUV absorption spectrum is temperature dependent, and nonradiative recombination converts the initial electronic excitation to thermal excitation within picoseconds. Ultrafastmore » electron diffraction (UED) is used to measure the lattice temperature and confirm the recombination mechanism. Lastly, the XUV and UED results support a 2nd-order recombination model with a rate constant of 2.5x10 -9 cm 3/s.« less

Light-induced absorption and its relaxation under illumination of continuous wave ultraviolet light in Mn-doped near-stoichiometric LiNbO{sub 3}

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu Youwen; Kitamura, Kenji; Takekawa, Shunji

2005-04-01

The steady-state light-induced absorption and the temporal relaxation behavior under illumination of cw ultraviolet light in Mn-doped near-stoichiometric LiNbO{sub 3} with different crystal compositions are investigated. The ultraviolet-light-induced absorption has been assigned to small polarons Nb{sub Li}{sup 4+} by measuring the absorption spectra at room temperature. The dependences of relaxation behaviors (time constant and stretching factor) of light-induced absorption on various illumination conditions (intensity, polarization) and temperature are presented, which are very different from those observed in Fe-doped LiNbO{sub 3} illuminated with highly intense light pulse, though the temporal relaxation follows the same stretched-exponential decay behavior in both cases. Themore » results are explained reasonably by using the model of distance-dependent electron transition probabilities between localized deep traps and small polarons without any additional assumptions, and discussed to tailor doped near-stoichiometric LiNbO{sub 3} crystals for two-color holographic recording with cw laser light.« less

Spectral parameters and Hamaker constants of silicon hydride compounds and organic solvents.

PubMed

Masuda, Takashi; Matsuki, Yasuo; Shimoda, Tatsuya

2009-12-15

Cyclopentasilane (CPS) and polydihydrosilane, which consist of hydrogen and silicon only, are unique materials that can be used to produce intrinsic silicon film in a liquid process, such as spin coating or an ink-jet method. Wettability and solubility of general organic solvents including the above can be estimated by Hamaker constants, which are calculated according to the Lifshitz theory. In order to calculate a Hamaker constant by the simple spectral method (SSM), it is necessary to obtain absorption frequency and function of oscillator strength in the ultraviolet region. In this report, these physical quantities were obtained by means of an optical method. As a result of examination of the relation between molecular structures and ultraviolet absorption frequencies, which were obtained from various liquid materials, it was concluded that ultraviolet absorption frequencies became smaller as electrons were delocalized. In particular, the absorption frequencies were found to be very small for CPS and polydihydrosilane due to sigma-conjugate of their electrons. The Hamaker constants of CPS and polydihydrosilane were successfully calculated based on the obtained absorption frequency and function of oscillator strength.

Evaluation of Low-Earth-Orbit Environmental Effects on International Space Station Thermal Control Materials

NASA Technical Reports Server (NTRS)

Dever, Joyce A.

1998-01-01

Many spacecraft thermal control coatings in low Earth orbit (LEO) can be affected by solar ultraviolet radiation and atomic oxygen. Ultraviolet radiation can darken some polymers and oxides commonly used in thermal control materials. Atomic oxygen can erode polymer materials, but it may reverse the ultraviolet-darkening effect on oxides. Maintaining the desired solar absorptance for thermal control coatings is important to assure the proper operating temperature of the spacecraft. Thermal control coatings to be used on the International Space Station (ISS) were evaluated for their performance after exposure in the NASA Lewis Research Center's Atomic Oxygen-Vacuum Ultraviolet Exposure (AO-VUV) facility. This facility simulated the LEO environments of solar vacuum ultraviolet (VUV) radiation (wavelength range, 115 to 200 nanometers (nm)) and VUV combined with atomic oxygen. Solar absorptance was measured in vacuo to eliminate the "bleaching" effects of ambient oxygen on VUV-induced degradation. The objective of these experiments was to determine solar absorptance increases of various thermal control materials due to exposure to simulated LEO conditions similar to those expected for ISS. Work was done in support of ISS efforts at the requests of Boeing Space and Defense Systems and Lockheed Martin Vought Systems.

A survey of local interstellar hydrogen from OAO-2 observations of Lyman alpha absorption

NASA Technical Reports Server (NTRS)

Savage, B. D.; Jenkins, E. B.

1972-01-01

The Wisconsin far ultraviolet spectrometer aboard OAO-2 observed the wavelength region near 1216 A for 69 stars of spectral type B2 or earlier. From the strength of the observed interstellar L sub alpha absorption, atomic hydrogen column densities were derived over distances averaging 300 pc away from the sun. The OAO data were compared to synthetic ultraviolet spectra, originally derived from earlier higher resolution rocket observations, which were computer processed to simulate the effects of absorption by different amounts of hydrogen followed by the instrumental blending.

Absorption of Dy3+ and Nd3+ ions in Ba R 2F8 single crystals

NASA Astrophysics Data System (ADS)

Apollonov, V. V.; Pushkar', A. A.; Uvarova, T. V.; Chernov, S. P.

2008-09-01

The Dy3+ absorption and excitation spectra of BaY2F8 and BaYb2F8 single crystals are investigated in the ultraviolet, vacuum ultraviolet, and visible ranges at a temperature of 300 K. These crystals exhibit intense broad absorption bands due to the spin-allowed 4 f-5 d transitions in the range (56-78) × 10-3 cm-1 and less intense absorption bands that correspond to the spin-forbidden transitions in the range (50-56) × 10-3 cm-1. The Nd3+ absorption spectra of BaY2F8 single crystals are studied in the range (34-82) × 10-3 cm-1 at 300 K for different crystal orientations.

A Fourier transform spectrometer for visible and near ultra-violet measurements of atmospheric absorption

NASA Technical Reports Server (NTRS)

Parsons, C. L.; Gerlach, J. C.; Whitehurst, M.

1982-01-01

The development of a prototype, ground-based, Sun-pointed Michelson interferometric spectrometer is described. Its intended use is to measure the atmospheric amount of various gases which absorb in the near-infrared, visible, and near-ultraviolet portions of the electromagnetic spectrum. Preliminary spectra which contain the alpha, 0.8 micrometer, and rho sigma tau water vapor absorption bands in the near-infrared are presented to indicate the present capability of the system. Ultimately, the spectrometer can be used to explore the feasible applications of Fourier transform spectroscopy in the ultraviolet where grating spectrometers were used exclusively.

40 CFR 796.1050 - Absorption in aqueous solution: Ultraviolet/visible spectra.

Code of Federal Regulations, 2013 CFR

2013-07-01

... by both molar absorption coefficient (molar extinction coefficient) and band width. However, the..., expressed in cm; and the molar absorption (extinction) coefficient,εi, of each species. The absorbance...

40 CFR 796.1050 - Absorption in aqueous solution: Ultraviolet/visible spectra.

Code of Federal Regulations, 2012 CFR

2012-07-01

... by both molar absorption coefficient (molar extinction coefficient) and band width. However, the..., expressed in cm; and the molar absorption (extinction) coefficient,εi, of each species. The absorbance...

40 CFR 796.1050 - Absorption in aqueous solution: Ultraviolet/visible spectra.

Code of Federal Regulations, 2014 CFR

2014-07-01

... by both molar absorption coefficient (molar extinction coefficient) and band width. However, the..., expressed in cm; and the molar absorption (extinction) coefficient,εi, of each species. The absorbance...

Physical Conditions in the Ultraviolet Absorbers of IRAS F22456-5125

NASA Astrophysics Data System (ADS)

Dunn, Jay P.; Crenshaw, D. Michael; Kraemer, S. B.; Trippe, M. L.

2010-04-01

We present the ultraviolet (UV) and X-ray spectra observed with the Far Ultraviolet Spectroscopic Explorer (FUSE) and the XMM-Newton satellite, respectively, of the low-z Seyfert 1 galaxy IRAS F22456 - 5125. This object shows absorption from five distinct, narrow kinematic components that span a significant range in velocity (~0 to -700 km s-1) and ionization (Lyman series, C III, N III, and O VI). We also show that three of the five kinematic components in these lines appear to be saturated in Lyβ λ1026 and that all five components show evidence of saturation in the O VI doublet lines λλ1032, 1038. Further, all five components show evidence for partial covering due to the absorption seen in the O VI doublet. This object is peculiar because it shows no evidence for corresponding X-ray absorption to the UV absorption in the X-ray spectrum, which violates the 1:1 correlation known for low-z active galactic nuclei (AGNs). We perform photoionization modeling of the UV absorption lines and predict that the O VII column density should be small, which would produce little to no absorption in agreement with the X-ray observation. We also examine the UV variability of the continuum flux for this object (an increase of a factor of 6). As the absorption components lack variability, we find a lower limit of ~20 kpc for the distance for the absorbers from the central AGN. Based on observations made with the NASA-CNES-CSA Far Ultraviolet Spectroscopic Explorer. FUSE is operated for NASA by the Johns Hopkins University under NASA contract NAS5-32985.

A survey of ultraviolet interstellar absorption lines

NASA Technical Reports Server (NTRS)

Bohlin, R. C.; Jenkins, E. B.; Spitzer, L., Jr.; York, D. G.; Hill, J. K.; Savage, B. D.; Snow, T. P., Jr.

1983-01-01

A telescope-spectrometer on the Copernicus spacecraft made possible the measurement of many ultraviolet absorption lines produced by the interstellar gas. The present survey provides data on ultraviolet absorption lines in the spectra of 88 early-type stars. The stars observed are divided into four classes, including reddened stars, unreddened bright stars, moderately reddened bright stars, and unreddened and moderately reddened faint stars. Data are presented for equivalent width, W, radial velocity V, and rms line width, D, taking into account some 10 to 20 lines of N I, O I, Si II, P II, S II, Cl I, Cl II, Mn II, Fe II, Ni II, Cu II, and H2. The data are based on multiple scans for each line. Attention is given to details of observations, the data reduction procedure, and the computation of equivalent width, mean velocity, and velocity dispersion.

Changes in the near edge X-ray absorption fine structure of hybrid organic-inorganic resists upon exposure.

PubMed

Fallica, Roberto; Watts, Benjamin; Roesner, Benedikt; Della Giustina, Gioia; Brigo, Laura; Brusatin, Giovanna; Ekinci, Yasin

2018-06-14

We report on the near edge X-ray absorption fine structure (NEXAFS) spectroscopy of hybrid organic-inorganic resists. These materials are nonchemically amplified systems based on Si, Zr, and Ti oxides, synthesized from organically modified precursors and transition metal alkoxides by a sol-gel route and designed for ultraviolet, extreme ultraviolet and electron beam lithography. The experiments were conducted using a scanning transmission X-ray microscope (STXM) which combines high spatial-resolution microscopy and NEXAFS spectroscopy. The absorption spectra were collected in the proximity of the carbon edge (~ 290 eV) before and after in situ exposure, enabling the measurement of a significant photo-induced degradation of the organic group (phenyl or methyl methacrylate, respectively), the degree of which depends on the configuration of the ligand. Photo-induced degradation was more efficient in the resist synthesized with pendant phenyl substituents than it was in the case of systems based on bridging phenyl groups. The degradation of the methyl methacrylate group was relatively efficient, with about half of the initial ligands dissociated upon exposure. Our data reveal that the such dissociation can produce different outcomes, depending on the structural configuration. While all the organic groups were expected to detach and desorb from the resist in their entirety, a sizeable amount of them remain and form undesired byproducts such as alkene chains. In the framework of the materials synthesis and engineering through specific building blocks, these results provide a deeper insight into the photochemistry of resists, in particular for extreme ultraviolet lithography. © 2018 IOP Publishing Ltd.

Observations of the Ultraviolet Spectra of Carbon White Dwarfs

NASA Technical Reports Server (NTRS)

Wagner, G. A.

1982-01-01

Strong ultraviolet carbon lines were detected in additional white DC (continuous visual spectra) dwarfs using the IUE. These lines are not seen in the ultraviolet spectrum of the cool DC star Stein 2051 B. The bright DA white dwarf LB 3303 has a strong unidentified absorption near lambda 1400.

ASASSN-15LH: A SUPERLUMINOUS ULTRAVIOLET REBRIGHTENING OBSERVED BY SWIFT AND HUBBLE

DOE Office of Scientific and Technical Information (OSTI.GOV)

Brown, Peter J.; Yang, Yi; Wang, Lifan

2016-09-01

We present and discuss ultraviolet and optical photometry from the Ultraviolet/Optical Telescope, X-ray limits from the X-Ray Telescope on Swift, and imaging polarimetry and ultraviolet/optical spectroscopy with the Hubble Space Telescope , all from observations of ASASSN-15lh. It has been classified as a hydrogen-poor superluminous supernova (SLSN I), making it more luminous than any other supernova observed. ASASSN-15lh is not detected in the X-rays in individual or co-added observations. From the polarimetry we determine that the explosion was only mildly asymmetric. We find the flux of ASASSN-15lh to increase strongly into the ultraviolet, with an ultraviolet luminosity 100 times greatermore » than the hydrogen-rich, ultraviolet-bright SLSN II SN 2008es. We find that objects as bright as ASASSN-15lh are easily detectable beyond redshifts of ∼4 with the single-visit depths planned for the Large Synoptic Survey Telescope. Deep near-infrared surveys could detect such objects past a redshift of ∼20, enabling a probe of the earliest star formation. A late rebrightening—most prominent at shorter wavelengths—is seen about two months after the peak brightness, which is itself as bright as an SLSN. The ultraviolet spectra during the rebrightening are dominated by the continuum without the broad absorption or emission lines seen in SLSNe or tidal disruption events (TDEs) and the early optical spectra of ASASSN-15lh. Our spectra show no strong hydrogen emission, showing only Ly α absorption near the redshift previously found by optical absorption lines of the presumed host. The properties of ASASSN-15lh are extreme when compared to either SLSNe or TDEs.« less

Recent advances and applications of gas chromatography vacuum ultraviolet spectroscopy.

PubMed

Santos, Inês C; Schug, Kevin A

2017-01-01

The vacuum ultraviolet spectrophotometer was developed recently as an alternative to existing gas chromatography detectors. This detector measures the absorption of gas-phase chemical species in the range of 120-240 nm, where all chemical compounds present unique absorption spectra. Therefore, qualitative analysis can be performed and quantification follows standard Beer-Lambert law principles. Different fields of application, such as petrochemical, food, and environmental analysis have been explored. Commonly demonstrated is the capability for facile deconvolution of co-eluting analytes. The concept of additive absorption for co-eluting analytes has also been advanced for classification and speciation of complex mixtures using a data treatment procedure termed time interval deconvolution. Furthermore, pseudo-absolute quantitation can be performed for system diagnosis, as well as potentially calibrationless quantitation. In this manuscript an overview of these features, the vacuum ultraviolet spectrophotometer instrumentation, and performance capabilities are given. A discussion of the applications of the vacuum ultraviolet detector is provided by describing and discussing the papers published thus far since 2014. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Contribution of mycosporine-like amino acids and colored dissolved and particulate matter to sea ice optical properties and ultraviolet attenuation

PubMed Central

Uusikivi, Jari; Vähätalo, Anssi V.; Granskog, Mats A.; Sommaruga, Ruben

2010-01-01

In the Baltic Sea ice, the spectral absorption coefficients for particulate matter (PM) were about two times higher at ultraviolet wavelengths than at photosynthetically available radiation (PAR) wavelengths. PM absorption spectra included significant absorption by mycosporine-like amino acids (MAAs) between 320 and 345 nm. In the surface ice layer, the concentration of MAAs (1.37 μg L−1) was similar to that of chlorophyll a, resulting in a MAAs-to-chlorophyll a ratio as high as 0.65. Ultraviolet radiation (UVR) intensity and the ratio of UVR to PAR had a strong relationship with MAAs concentration (R2 = 0.97, n = 3) in the ice. In the surface ice layer, PM and especially MAAs dominated the absorption (absorption coefficient at 325 nm: 0.73 m−1). In the columnar ice layers, colored dissolved organic matter was the most significant absorber in the UVR (< 380 nm) (absorption coefficient at 325 nm: 1.5 m−1). Our measurements and modeling of UVR and PAR in Baltic Sea ice show that organic matter, both particulate and dissolved, influences the optical properties of sea ice and strongly modifies the UVR exposure of biological communities in and under snow-free sea ice. PMID:20585592

Discrimination of Medicine Radix Astragali from Different Geographic Origins Using Multiple Spectroscopies Combined with Data Fusion Methods

NASA Astrophysics Data System (ADS)

Wang, Hai-Yan; Song, Chao; Sha, Min; Liu, Jun; Li, Li-Ping; Zhang, Zheng-Yong

2018-05-01

Raman spectra and ultraviolet-visible absorption spectra of four different geographic origins of Radix Astragali were collected. These data were analyzed using kernel principal component analysis combined with sparse representation classification. The results showed that the recognition rate reached 70.44% using Raman spectra for data input and 90.34% using ultraviolet-visible absorption spectra for data input. A new fusion method based on Raman combined with ultraviolet-visible data was investigated and the recognition rate was increased to 96.43%. The experimental results suggested that the proposed data fusion method effectively improved the utilization rate of the original data.

Electronic absorption spectroscopy of matrix-isolated polycyclic aromatic hydrocarbon cations. I - The naphthalene cation (C10H8/+/)

NASA Technical Reports Server (NTRS)

Salama, F.; Allamandola, L. J.

1991-01-01

The ultraviolet, visible, and near-infrared absorption spectra of naphthalene (C10H8) and its radical ion (C10H8/+/), formed by vacuum ultraviolet irradiation, were measured in argon and neon matrices at 4.2 K. The associated vibronic band systems and their spectroscopic assignments are discussed together with the physical and chemical conditions governing ion production in the solid phase. The absorption coefficients were calculated for the ion and found lower than previous values, presumably due to the low polarizability of the neon matrix.

Ultraviolet absorption cross-sections of hot carbon dioxide

NASA Astrophysics Data System (ADS)

Oehlschlaeger, Matthew A.; Davidson, David F.; Jeffries, Jay B.; Hanson, Ronald K.

2004-12-01

The temperature-dependent ultraviolet absorption cross-section for CO 2 has been measured in shock-heated gases between 1500 and 4500 K at 216.5, 244, 266, and 306 nm. Continuous-wave lasers provide the spectral brightness to enable precise time-resolved measurements with the microsecond time-response needed to monitor thermal decomposition of CO 2 at temperatures above 3000 K. The photophysics of the highly temperature dependent cross-section is discussed. The new data allows the extension of CO 2 absorption-based temperature sensing methods to higher temperatures, such as those found in behind detonation waves.

Ultraviolet Spectrum And Chemical Reactivity Of CIO Dimer

NASA Technical Reports Server (NTRS)

Demore, William B.; Tschuikow-Roux, E.

1992-01-01

Report describes experimental study of ultraviolet spectrum and chemical reactivity of dimer of chlorine monoxide (CIO). Objectives are to measure absorption cross sections of dimer at near-ultraviolet wavelengths; determine whether asymmetrical isomer (CIOCIO) exists at temperatures relevant to Antarctic stratosphere; and test for certain chemical reactions of dimer. Important in photochemistry of Antarctic stratosphere.

REACTION OF AMINO-ACIDS AND PEPTIDE BONDS WITH FORMALDEHYDE AS MEASURED BY CHANGES IN THE ULTRA-VIOLET SPECTRA,

DTIC Science & Technology

AMINO ACIDS , CHEMICAL REACTIONS), (*PEPTIDES, CHEMICAL REACTIONS), (*FORMALDEHYDE, CHEMICAL REACTIONS), (*ULTRAVIOLET SPECTROSCOPY, PROTEINS), ABSORPTION SPECTRA, CHEMICAL BONDS, AMIDES, CHEMICAL EQUILIBRIUM, REACTION KINETICS

Reassignment of the Iron (3) Absorption Bands in the Spectra of Mars

NASA Technical Reports Server (NTRS)

Sherman, D. M.

1985-01-01

Absorption features in the near-infrared and visible region reflectance spectra of Mars have been assigned to specific Fe (3+) crystal-field and o(2-) yields Fe(3+) charge transfer transitions. Recently, near-ultraviolet absorption spectra of iron oxides were obtained and the energies of o(2-) yields Fe(3+) charge-transfer (LMCT) transitions were determined from accurate SCF-X # alpha-SW molecular orbital calculations on (FeO6)(9-) and (FeO4)(5-) clusters. Both the theoretical and experimental results, together with existing data in the literature, show that some of the previous Fe(3+) band assignments in the spectra of Mars need to be revised. The theory of Fe(3+) spectra in minerals is discussed and applied to the spectrum of Mars.

Computer-Graphics Emulation of Chemical Instrumentation: Absorption Spectrophotometers.

ERIC Educational Resources Information Center

Gilbert, D. D.; And Others

1982-01-01

Describes interactive, computer-graphics program emulating behavior of high resolution, ultraviolet-visible analog recording spectrophotometer. Graphics terminal behaves as recording absorption spectrophotometer. Objective of the emulation is study of optimization of the instrument to yield accurate absorption spectra, including…

Investigating the 3.3 micron infrared fluorescence from naphthalene following ultraviolet excitation

NASA Technical Reports Server (NTRS)

Williams, Richard M.; Leone, Stephen R.

1994-01-01

Polycyclic aromatic hydrocarbon (PAH) type molecules are proposed as the carriers of the unidentified infrared (UIR) bands. Detailed studies of the 3.3 micrometer infrared emission features from naphthalene, the simplest PAH, following ultraviolet laser excitation are used in the interpretation of the 3.29 micrometer (3040 cm(sup -1)) UIR band. A time-resolved Fourier transform spectrometer is used to record the infrared emission spectrum of gas-phase naphthalene subsequent to ultraviolet excitation facilitated by an excimer laser operated at either 193 nm or 248 nm. The emission spectra differ significantly from the absorption spectrum in the same spectral region. Following 193 nm excitation the maximum in the emission profile is red-shifted 45 cm(sup -1) relative to the absorption maximum; a 25 cm(sup -1) red-shift is observed after 248 nm excitation. The red-shifting of the emission spectrum is reduced as collisional and radiative relaxation removes energy from the highly vibrationally excited molecules. Coupling between the various vibrational modes is thought to account for the differences between absorption and emission spectra. Strong visible emission is also observed following ultraviolet excitation. Visible emission may play an important role in the rate of radiative relaxation, which according to the interstellar PAH hypothesis occurs only by the slow emission of infrared photons. Studying the visible emission properties of PAH type molecules may be useful in the interpretation of the DIB's observed in absorption.

Modelling ultraviolet-line diagnostics of stars, the ionized and the neutral interstellar medium in star-forming galaxies

NASA Astrophysics Data System (ADS)

Vidal-García, A.; Charlot, S.; Bruzual, G.; Hubeny, I.

2017-09-01

We combine state-of-the-art models for the production of stellar radiation and its transfer through the interstellar medium (ISM) to investigate ultraviolet-line diagnostics of stars, the ionized and the neutral ISM in star-forming galaxies. We start by assessing the reliability of our stellar population synthesis modelling by fitting absorption-line indices in the ISM-free ultraviolet spectra of 10 Large Magellanic Cloud clusters. In doing so, we find that neglecting stochastic sampling of the stellar initial mass function in these young (∼10-100 Myr), low-mass clusters affects negligibly ultraviolet-based age and metallicity estimates but can lead to significant overestimates of stellar mass. Then, we proceed and develop a simple approach, based on an idealized description of the main features of the ISM, to compute in a physically consistent way the combined influence of nebular emission and interstellar absorption on ultraviolet spectra of star-forming galaxies. Our model accounts for the transfer of radiation through the ionized interiors and outer neutral envelopes of short-lived stellar birth clouds, as well as for radiative transfer through a diffuse intercloud medium. We use this approach to explore the entangled signatures of stars, the ionized and the neutral ISM in ultraviolet spectra of star-forming galaxies. We find that, aside from a few notable exceptions, most standard ultraviolet indices defined in the spectra of ISM-free stellar populations are prone to significant contamination by the ISM, which increases with metallicity. We also identify several nebular-emission and interstellar-absorption features, which stand out as particularly clean tracers of the different phases of the ISM.

High-throughput ultraviolet photoacoustic microscopy with multifocal excitation

NASA Astrophysics Data System (ADS)

Imai, Toru; Shi, Junhui; Wong, Terence T. W.; Li, Lei; Zhu, Liren; Wang, Lihong V.

2018-03-01

Ultraviolet photoacoustic microscopy (UV-PAM) is a promising intraoperative tool for surgical margin assessment (SMA), one that can provide label-free histology-like images with high resolution. In this study, using a microlens array and a one-dimensional (1-D) array ultrasonic transducer, we developed a high-throughput multifocal UV-PAM (MF-UV-PAM). Our new system achieved a 1.6 ± 0.2 μm lateral resolution and produced images 40 times faster than the previously developed point-by-point scanning UV-PAM. MF-UV-PAM provided a readily comprehensible photoacoustic image of a mouse brain slice with specific absorption contrast in ˜16 min, highlighting cell nuclei. Individual cell nuclei could be clearly resolved, showing its practical potential for intraoperative SMA.

Gas chromatography-vacuum ultraviolet spectroscopy for analysis of fatty acid methyl esters.

PubMed

Fan, Hui; Smuts, Jonathan; Bai, Ling; Walsh, Phillip; Armstrong, Daniel W; Schug, Kevin A

2016-03-01

A new vacuum ultraviolet (VUV) detector for gas chromatography was recently developed and applied to fatty acid methyl ester (FAME) analysis. VUV detection features full spectral acquisition in a wavelength range of 115-240nm, where virtually all chemical species absorb. VUV absorption spectra of 37 FAMEs, including saturated, monounsaturated, and polyunsaturated types were recorded. Unsaturated FAMEs show significantly different gas phase absorption profiles than saturated ones, and these classes can be easily distinguished with the VUV detector. Another advantage includes differentiating cis/trans-isomeric FAMEs (e.g. oleic acid methyl ester and linoleic acid methyl ester isomers) and the ability to use VUV data analysis software for deconvolution of co-eluting signals. As a universal detector, VUV also provides high specificity, sensitivity, and a fast data acquisition rate, making it a powerful tool for fatty acid screening when combined with gas chromatography. The fatty acid profile of several food oil samples (olive, canola, vegetable, corn, sunflower and peanut oils) were analyzed in this study to demonstrate applicability to real world samples. Copyright © 2015 Elsevier Ltd. All rights reserved.

JPL Fourier transform ultraviolet spectrometer

NASA Technical Reports Server (NTRS)

Cageao, R. P.; Friedl, R. R.; Sander, Stanley P.; Yung, Y. L.

1994-01-01

The Fourier Transform Ultraviolet Spectrometer (FTUVS) is a new high resolution interferometric spectrometer for multiple-species detection in the UV, visible and near-IR. As an OH sensor, measurements can be carried out by remote sensing (limb emission and column absorption), or in-situ sensing (long-path absorption or laser-induced fluorescence). As a high resolution detector in a high repetition rate (greater than 10 kHz) LIF system, OH fluorescence can be discriminated against non-resonant background emission and laser scatter, permitting (0, 0) excitation.

Light absorption of organic aerosol from pyrolysis of corn stalk

NASA Astrophysics Data System (ADS)

Li, Xinghua; Chen, Yanju; Bond, Tami C.

2016-11-01

Organic aerosol (OA) can absorb solar radiation in the low-visible and ultra-violet wavelengths thereby modifying radiative forcing. Agricultural waste burning emits a large quantity of organic carbon in many developing countries. In this work, we improved the extraction and analysis method developed by Chen and Bond, and extended the spectral range of OC absorption. We examined light absorbing properties of primary OA from pyrolysis of corn stalk, which is a major type of agricultural wastes. Light absorption of bulk liquid extracts of OA was measured using a UV-vis recording spectrophotometer. OA can be extracted by methanol at 95%, close to full extent, and shows polar character. Light absorption of organic aerosol has strong spectral dependence (Absorption Ångström exponent = 7.7) and is not negligible at ultra-violet and low-visible regions. Higher pyrolysis temperature produced OA with higher absorption. Imaginary refractive index of organic aerosol (kOA) is 0.041 at 400 nm wavelength and 0.005 at 550 nm wavelength, respectively.

Influence of environmental factors on spectral characteristics of chromophoric dissolved organic matter (CDOM) in Inner Mongolia Plateau, China

NASA Astrophysics Data System (ADS)

Wen, Z. D.; Song, K. S.; Zhao, Y.; Du, J.; Ma, J. H.

2016-02-01

Spectral characteristics of chromophoric dissolved organic matter (CDOM) were examined in conjunction with environmental factors in the waters of rivers and terminal lakes within the Hulun Buir plateau, northeast China. Dissolved organic carbon (DOC), total nitrogen (TN), and total phosphorous (TP) were significantly higher in terminal lakes than rivers waters (p < 0.01). Principal component analysis (PCA) indicated that non-water light absorption and anthropogenic nutrient disturbances were the likely causes of the diversity of water quality parameters. CDOM absorption in river waters was significantly lower than terminal lakes. Analysis of the ratio of absorption at 250 to 365 nm (E250 : 365), specific ultraviolet (UV) absorbance (SUVA254), and the spectral slope ratio (Sr) indicated that CDOM in river waters had higher aromaticity, molecular weight, and vascular plant contribution than in terminal lakes. Furthermore, results showed that DOC concentration, CDOM light absorption, and the proportion of autochthonous sources of CDOM in plateau waters were all higher than in other freshwater rivers reported in the literature. The strong evapoconcentration, intense ultraviolet irradiance, and landscape features of the Hulun Buir plateau may be responsible for the above phenomenon. Redundancy analysis (RDA) indicated that the environmental variables total suspended matter (TSM), TN, and electrical conductivity (EC) had a strong correlation with light absorption characteristics, followed by total dissolved solid (TDS) and chlorophyll a. In most sampling locations, CDOM was the dominant non-water light-absorbing substance. Light absorption by non-algal particles often exceeded that by phytoplankton in the plateau waters. Study of these optical-physicochemical correlations is helpful in the evaluation of the potential influence of water quality factors on non-water light absorption in cold plateau water environments. The construction of a correlation between DOC concentration and water quality factors may help contribute to regional estimates of carbon sources and fate for catchment carbon budget assessments.

Weighing the Low-Redshift Lyman-alpha Forest

NASA Technical Reports Server (NTRS)

Shull, Mike

2005-01-01

In 2003-2004, our FUSE research group prepared several major surveys of the amount of baryonic matter in the intergalactic medium (IGM), using the Far Ultraviolet Spectroscopic Explorer (FUSE) satellite. These surveys include measurements of the Lyman-alpha absorption line of neutral hydrogen (H I), the far-ultraviolet (1032,1038 Angstrom) doublet of highly ionized oxygen ( O VI), the higher Lyman-series lines (Ly-beta, Ly-gamma, etc) of H I, and the 977 Angstrom line of c III. As an overview, our FUSE spectroscopic studies, taken together with data from the Hubble Space Telescope, show that approximately 30% of the normal matter is contained in intergalactic hydrogen gas clouds (the Lyman-alpha forest). Another 5-10% resides in hotter gas at temperatures of 10(exp 5) to 10(exp 6) K, visible in 0 VI and C III absorption. Along with the matter attributed to galaxies, we have now accounted for approximately HALF of all the baryonic matter in the universe. Where is the other half? That matter my exist in even hotter gas, invisible through the ultraviolet absorption lines, but perhaps detectable through X-ray absorption lines of more highly ionized oxygen and neon.

Development of vacuum ultraviolet absorption spectroscopy system for wide measurement range of number density using a dual-tube inductively coupled plasma light source

NASA Astrophysics Data System (ADS)

Kuwahara, Akira; Matsui, Makoto; Yamagiwa, Yoshiki

2012-12-01

A vacuum ultraviolet absorption spectroscopy system for a wide measurement range of atomic number densities is developed. Dual-tube inductively coupled plasma was used as a light source. The probe beam profile was optimized for the target number density range by changing the mass flow rate of the inner and outer tubes. This system was verified using cold xenon gas. As a result, the measurement number density range was extended from the conventional two orders to five orders of magnitude.

What Fraction of Active Galaxies Actually Show Outflows?

NASA Astrophysics Data System (ADS)

Ganguly, Rajib; Brotherton, M. S.

2007-12-01

Outflows from active galactic nuclei (AGNs) seem to be common and are thought to be important from a variety of perspectives: as an agent of chemical enhancement of the interstellar and intergalactic media, as an agent of angular momentum removal from the accreting central engine, and as an agent limiting star formation in starbursting systems by blowing out gas and dust from the host galaxy. To understand these processes, we must determine what fraction of AGNs feature outflows and understand what forms they take. We examine recent surveys of outflows detected in ultraviolet absorption over the entire range of velocities and velocity widths (i.e., broad absorption lines, associated absorption lines, and high-velocity narrow absorption lines). While the fraction of specific forms of outflows depends on AGN properties, the overall fraction displaying outflows is fairly constant, approximately 60%, over many orders of magnitude in luminosity. We discuss implications of this result and ways to refine our understanding of outflows. We acknowledge support from the US National Science Foundation through grant AST 05-07781.

Saving Your Students' Skin. Undergraduate Experiments that Probe UV Protection by Sunscreens and Sunglasses

NASA Astrophysics Data System (ADS)

Abney, James R.; Scalettar, Bethe A.

1998-06-01

Recent scientific evidence suggests that chlorofluorocarbons have substantially depleted the ozone layer, the earth's primary filter for ultraviolet radiation. At the same time, medical evidence has accumulated which suggests that exposure to ultraviolet radiation is a major cause of prevalent human health disorders, including skin cancer and cataracts. For these reasons, consumer purchases of sunscreens and sunglasses, which provide protection from ultraviolet radiation, have soared, and manufacturer interest in improving these products has intensified. This article describes absorption spectroscopy experiments that illustrate the mechanism of action of sunscreens and sunglasses and that highlight the differences between different products. The experiments are well suited to incorporation into an undergraduate science laboratory and will expose students to absorption phenomena in a familiar context with substantial environmental and medical relevance.

Fluorescence of molecular hydrogen excited by solar extreme-ultraviolet radiation

NASA Technical Reports Server (NTRS)

Feldman, P. D.; Fastie, W. G.

1973-01-01

During trans-earth coast, the Apollo 17 ultraviolet spectrometer was scheduled to make observations of the far ultraviolet background in selected regions of the sky. In the course of one of these observations, the spacecraft fuel cells were routinely purged of excess hydrogen and water vapor. The ultraviolet fluorescence spectrum of the purged molecular hydrogen excited by solar extreme ultraviolet radiation is interpreted by absorption of solar L-beta and L-gamma radiation in the nearly resonant (6, 0) and (11, 0) Lyman bands. The results are deemed significant for ultraviolet spectroscopic investigations of the atmospheres of the moon and planets since Lyman-band fluorescence provides an unambiguous means of identification of molecular hydrogen in upper atmospheres.

INTERACTIONS OF SOLAR ULTRAVIOLET RADIATION AND DISSOLVED ORGANIC MATTER IN FRESHWATER AND MARINE ENVIRONMENTS

EPA Science Inventory

Solar radiation provides the primary driving force for the biogeochemical cycles upon which life and climate depend. Recent studies have demonstrated that the absorption of solar radiation, especially 'm the ultraviolet spectral region, results in photochemical reactions that can...

Extreme ultraviolet observations of G191-B2B and the local interstellar medium with the Hopkins Ultraviolet Telescope

NASA Technical Reports Server (NTRS)

Kimble, Randy A.; Davidsen, Arthur F.; Blair, William P.; Bowers, Charles W.; Van Dyke Dixon, W.; Durrance, Samuel T.; Feldman, Paul D.; Ferguson, Henry C.; Henry, Richard C.; Kriss, Gerard A.

1993-01-01

During the Astro-l mission in 1990 December, the Hopkins Ultraviolet Telescope (HUT) was used to observe the extreme ultraviolet spectrum (415-912 A) of the hot DA white dwarf GI91-B2B. Absorption by neutral helium shortward of the 504 A He I absorption edge is clearly detected in the raw spectrum. Model fits to the observed spectrum require interstellar neutral helium and neutral hydrogen column densities of 1.45 +/- 0.065 x 10 exp 17/sq cm and 1.69 +/- 0.12 x 10 exp 18/sq cm, respectively. Comparison of the neutral columns yields a direct assessment of the ionization state of the local interstellar cloud surrounding the Sun. The neutral hydrogen to helium ratio of 11.6 +/- 1.0 observed by HUT strongly contradicts the widespread view that hydrogen is much more ionized than helium in the local interstellar medium, a view which has motivated some exotic theoretical explanations for the supposed high ionization.

A Hubble Space Telescope Survey of Intrinsic Absorption in Nearby AGN

NASA Astrophysics Data System (ADS)

Dashtamirova, Dzhuliya; Dunn, Jay P.; Crenshaw, D. Michael

2017-01-01

We present a survey of the intrinsic UV absorption lines in active galactic nuclei (AGN). We limit our study to the ultraviolet spectra of type 1 AGN with a redshift of z < 0.15 as a continuation of the Dunn et al. (2007, 2008) and Crenshaw et al. (1999) studies of smaller samples. We identify approximately 90 AGN fit our redshift specifications in the Mikulski Archive for Space Telescopes (MAST) database with Cosmic Origin Spectrograph (COS) observations. We download and co-add all of the COS spectra. We find that about 80 of these are type 1 AGN. We normalize the COS spectra and identify all of the intrinsic Lyman-alpha, N V, Si IV, and C IV intrinsic absorption features. From these data, we determine the fraction of type 1 AGN with intrinsic absorption in this redshift range and find the global covering factors of the absorbers. We also identify low ionization species as well as excited state lines. A number of objects have multiple epoch COS and/or Space Telescope Imaging Spectrograph (STIS) observations, which we use to investigate the absorption variability.

Characterization of photoluminescence spectra from poly allyl diglycol carbonate (CR-39) upon excitation with the ultraviolet radiation of various wavelengths

NASA Astrophysics Data System (ADS)

El Ghazaly, M.; Al-Thomali, Talal A.

2013-04-01

The induced photoluminescence (PL) from the π-conjugated polymer poly allyl diglycol carbonate (PADC) (CR-39) upon excitation with the ultraviolet radiation of different wavelengths was investigated. The absorption and attenuation coefficients of PADC (CR-39) were recorded using a UV-visible spectrometer. It was found that the absorption and attenuation coefficients of the PADC (CR-39) exhibit a strong dependence on the wavelength of ultraviolet radiation. The PL spectra were measured with a Flormax-4 spectrofluorometer (Horiba). PADC (CR-39) samples were excited by ultraviolet radiation with wavelengths in the range from 260 to 420 nm and the corresponding PL emission bands were recorded. The obtained results show a strong correlation between the PL and the excitation wavelength of ultraviolet radiation. The position of the fluorescence emission band peak was red shifted starting from 300 nm, which was increased with the increase in the excitation wavelength. The PL yield and its band peak height were increased with the increase in the excitation wavelength till 290 nm, thereafter they decreased exponentially with the increase in the ultraviolet radiation wavelength. These new findings should be considered carefully during the use of the PADC (CR-39) in the scientific applications and in using PADC (CR-39) in eyeglasses.

Attosecond transient absorption of argon atoms in the vacuum ultraviolet region: line energy shifts versus coherent population transfer

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cao, Wei; Warrick, Erika R.; Neumark, Daniel M.

Using attosecond transient absorption, the dipole response of an argon atom in the vacuum ultraviolet (VUV) region is studied when an external electromagnetic field is present. An isolated attosecond VUV pulse populates Rydberg states lying 15 eV above the argon ground state. A synchronized few-cycle near infrared (NIR) pulse modifies the oscillating dipoles of argon impulsively, leading to alterations in the VUV absorption spectra. As the NIR pulse is delayed with respect to the VUV pulse, multiple features in the absorption profile emerge simultaneously including line broadening, sideband structure, sub-cycle fast modulations, and 5-10 fs slow modulations. These features indicatemore » the coexistence of two general processes of the light-matter interaction: the energy shift of individual atomic levels and coherent population transfer between atomic eigenstates, revealing coherent superpositions. Finally, an intuitive formula is derived to treat both effects in a unifying framework, allowing one to identify and quantify the two processes in a single absorption spectrogram.« less

Attosecond transient absorption of argon atoms in the vacuum ultraviolet region: line energy shifts versus coherent population transfer

NASA Astrophysics Data System (ADS)

Cao, Wei; Warrick, Erika R.; Neumark, Daniel M.; Leone, Stephen R.

2016-01-01

Using attosecond transient absorption, the dipole response of an argon atom in the vacuum ultraviolet (VUV) region is studied when an external electromagnetic field is present. An isolated attosecond VUV pulse populates Rydberg states lying 15 eV above the argon ground state. A synchronized few-cycle near infrared (NIR) pulse modifies the oscillating dipoles of argon impulsively, leading to alterations in the VUV absorption spectra. As the NIR pulse is delayed with respect to the VUV pulse, multiple features in the absorption profile emerge simultaneously including line broadening, sideband structure, sub-cycle fast modulations, and 5-10 fs slow modulations. These features indicate the coexistence of two general processes of the light-matter interaction: the energy shift of individual atomic levels and coherent population transfer between atomic eigenstates, revealing coherent superpositions. An intuitive formula is derived to treat both effects in a unifying framework, allowing one to identify and quantify the two processes in a single absorption spectrogram.

Attosecond transient absorption of argon atoms in the vacuum ultraviolet region: line energy shifts versus coherent population transfer

DOE PAGES

Cao, Wei; Warrick, Erika R.; Neumark, Daniel M.; ...

2016-01-18

Using attosecond transient absorption, the dipole response of an argon atom in the vacuum ultraviolet (VUV) region is studied when an external electromagnetic field is present. An isolated attosecond VUV pulse populates Rydberg states lying 15 eV above the argon ground state. A synchronized few-cycle near infrared (NIR) pulse modifies the oscillating dipoles of argon impulsively, leading to alterations in the VUV absorption spectra. As the NIR pulse is delayed with respect to the VUV pulse, multiple features in the absorption profile emerge simultaneously including line broadening, sideband structure, sub-cycle fast modulations, and 5-10 fs slow modulations. These features indicatemore » the coexistence of two general processes of the light-matter interaction: the energy shift of individual atomic levels and coherent population transfer between atomic eigenstates, revealing coherent superpositions. Finally, an intuitive formula is derived to treat both effects in a unifying framework, allowing one to identify and quantify the two processes in a single absorption spectrogram.« less

Saving Your Students' Skin. Undergraduate Experiments That Probe UV Protection by Sunscreens and Sunglasses.

ERIC Educational Resources Information Center

Abney, James R.; Scalettar, Bethe A.

1998-01-01

Describes absorption spectroscopy experiments that allow students to explore the mechanisms by which sunscreens and sunglasses provide protection from ultraviolet radiation. Exposes students to absorption phenomena in an engaging way. (DDR)

Vacuum Ultraviolet Absorption Measurements of Atomic Oxygen in a Shock Tube

NASA Technical Reports Server (NTRS)

Meyer, Scott Andrew

1995-01-01

The absorption of vacuum ultraviolet light by atomic oxygen has been measured in the Electric Arc-driven Shock Tube (EAST) Facility at NASA-Ames Research Center. This investigation demonstrates the instrumentation required to determine atomic oxygen concentrations from absorption measurements in impulse facilities. A shock wave dissociates molecular oxygen, producing a high temperature sample of atomic oxygen in the shock tube. A probe beam is generated with a Raman-shifted ArF excimer laser. By suitable tuning of the laser, absorption is measured over a range of wavelengths in the region of the atomic line at 130.49 nm. The line shape function is determined from measurements at atomic oxygen densities of 3 x 10(exp 17) and 9 x 10(exp 17)/cu cm. The broadening coefficient for resonance interactions is deduced from this data, and this value is in accord with available theoretical models.

Vacuum Ultraviolet Absorption Measurements of Atomic Oxygen in a Shock Tube

NASA Technical Reports Server (NTRS)

Meyer, Scott Andrew

1995-01-01

The absorption of vacuum ultraviolet light by atomic oxygen has been measured in the Electric Arc-driven Shock Tube (EAST) Facility at NASA-Ames Research Center. This investigation demonstrates the instrumentation required to determine atomic oxygen concentrations from absorption measurements in impulse facilities. A shock wave dissociates molecular oxygen, producing a high temperature sample of atomic oxygen in the shock tube. A probe beam is generated with a Raman-shifted ArF excimer laser. By suitable tuning of the laser, absorption is measured over a range of wavelengths in the region of the atomic line at 130.49 nm. The line shape function is determined from measurements at atomic oxygen densities of 3x10(exp 17) and 9x10(exp 17) cm(exp -3). The broadening coefficient for resonance interactions is deduced from this data, and this value is in accord with available theoretical models.

Vacuum Ultraviolet Absorption Measurements of Atomic Oxygen in a Shock Tube

NASA Technical Reports Server (NTRS)

Meyer, Scott Andrew

1995-01-01

The absorption of vacuum ultraviolet light by atomic oxygen has been measured in the Electric Arc-driven Shock Tube (EAST) Facility at NASA-Ames Research Center. This investigation demonstrates the instrumentation required to determine atomic oxygen concentrations from absorption measurements in impulse facilities. A shock wave dissociates molecular oxygen, producing a high temperature sample of atomic oxygen in the shock tube. A probe beam is generated with a Raman-shifted ArF excimer laser. By suitable tuning of the laser, absorption is measured over a range of wavelengths in the region of the atomic line at 130.49 nm. The line shape function is determined from measurements at atomic oxygen densities of 3 x 10(exp 17) and 9 x 10(exp 17) cm(exp -3). The broadening coefficient for resonance interactions is deduced from this data, and this value is in accord with available theoretical models.

The effect of Cd substitution doping on the bandgap and absorption spectrum of ZnO

NASA Astrophysics Data System (ADS)

Hou, Qingyu; Li, Yong; Qu, Lingfeng; Zhao, Chunwang

2016-08-01

Many research papers have reported that in the ultraviolet area of 290-360 nm wavelength range, blueshift and redshift in the absorption spectrum occurred in ZnO with Cd doping; however, there is no reasonable theoretical explanation to this so far. To solve this problem, this study investigates the differences of blueshift and redshift in doping system by adopting plane-wave ultrasoft pseudopotential technology based on the density functional theory and applying LDA + U method to calculate band structures, density of states and absorption spectrum distribution of the models, which is on the basis of model geometry optimization. By increasing the Cd doping concentration, the following results are obtained: increased volume of the mixed system, raised total energy, a decrease in stability, narrowed bandgaps and a significant redshift in the absorption spectrum in the ultraviolet or visible light area.

[The negative temperature effect of UV absorbance on C60 in different solvents].

PubMed

Yang, Tao; Zeng, Fan-qin; Ge, Qi; Xiong, Qian; Guo, Feng; Zhang, Xun-gao

2004-02-01

Ultraviolet Absorption Spectrum of Difference in Temperature (UVSDT) of C60 was studied in different solvents by UV-240 ultraviolet-visible spectrophotometer. Two samples were tested, one of which acted as reference sample and the other as ready test sample. During the period of the experiment, the temperature of the reference sample remained constant, while that of the ready test sample was changed to obtain difference in temperature. The two samples were scanned in succession by UV-240 ultraviolet-visible spectrophotometer using a certain range of wavelength. By changing the temperature of the ready test sample, we can get the ultraviolet absorption spectrum changing curve with temperature differential. In addition, the curve was studied by putting C60 in different solvents (alcohol, cyclohexane, n-hexane and 2-propanol). The curve indicates that the intensity of the absorption peak wavelength of C60 decreased with increasing the temperature of the sample, and a negative peak was observed in UVSDT. And the greater the difference in temperature, the higher the intensity of the negative peak. The result reflects that the structure of C60 depends strongly on its temperature, and the dependent relationship is closely related to the type of pi-pi electron transition. So it's valuable to test the absorption rate of C60 and obtain the changing curve in real time. It'll help us to separate, purify, analyze, and characterize C60. And it'll also help to do research on the mechanism of the chemical reactions, which take place in solvents, as well as to improve veracity.

Far-ultraviolet spectral changes of titanium dioxide with gold nanoparticles by ultraviolet and visible light

NASA Astrophysics Data System (ADS)

Tanabe, Ichiro; Kurawaki, Yuji

2018-05-01

Attenuated total reflectance spectra including the far-ultraviolet (FUV, ≤ 200 nm) region of titanium dioxide (TiO2) with and without gold (Au) nanoparticles were measured. A newly developed external light-irradiation system enabled to observe spectral changes of TiO2 with Au nanoparticles upon light irradiations. Absorption in the FUV region decreased and increased by the irradiation with ultraviolet and visible light, respectively. These spectral changes may reflect photo-induced electron transfer from TiO2 to Au nanoparticles under ultraviolet light and from Au nanoparticles to TiO2 under visible light, respectively.

A recent time of minimum for and atmospheric-eclipse in the ultraviolet spectrum of the Wolf-Rayet eclipsing binary V444 Cygni

NASA Technical Reports Server (NTRS)

Eaton, J. E.; Cherepashchuk, A. M.; Khaliullin, K. F.

1982-01-01

The 1200-1900 angstrom region and fine error sensor observations in the optical for V444 Cyg were continuously observed. More than half of a primary minimum and almost a complete secondary minimum were observed. It is found that the time of minimum for the secondary eclipse is consistent with that for primary eclipse, and the ultraviolet times of minimum are consistent with the optical ones. The spectrum shows a considerable amount of phase dependence. The general shaps and depths of the light curves for the FES signal and the 1565-1900 angstrom continuum are similar to those for the blue continuum. The FES, however, detected an atmospheric eclipse in line absorption at about the phase the NIV absorption was strongest. It is suggested that there is a source of continuum absorption shortward of 1460 angstrom which exists throughout a large part of the extended atmosphere and which, by implication, must redden considerably the ultraviolet continuua of WN stars. A fairly high degree of ionization for the inner part of the WN star a atmosphere is implied.

Chemical characterization of some aqueous leachates from crop residues in 'CELSS'

NASA Technical Reports Server (NTRS)

Madsen, Brooks C.

1992-01-01

Aqueous leachate samples prepared from crop residues that are produced as a component of the Controlled Ecological Life Support System program designed to support long duration space missions have been compared and general chemical characterization has been accomplished. Solid phase extraction and high performance liquid chromatography were used to accomplish comparisons based on chromatographic and ultraviolet absorption properties of the components that are present. Specific compounds were not identified, however, general composition related to the presence of phenol-like compounds was explored.

Dynamics of defects in Ce³⁺ doped silica affecting its performance as protective filter in ultraviolet high-power lasers.

PubMed

Demos, Stavros G; Ehrmann, Paul R; Qiu, S Roger; Schaffers, Kathleen I; Suratwala, Tayyab I

2014-11-17

We investigate defects forming in Ce³⁺-doped fused silica samples following exposure to nanosecond ultraviolet laser pulses and their relaxation as a function of time and exposure to low intensity light at different wavelengths. A subset of these defects are responsible for inducing absorption in the visible and near infrared spectral range, which is of critical importance for the use of this material as ultraviolet light absorbing filter in high power laser systems. The dependence of the induced absorption as a function of laser fluence and methods to most efficiently mitigate this effect are presented. Experiments simulating the operation of the material as a UV protection filter for high power laser systems were performed in order to determine limitations and practical operational conditions.

Environmental phototoxicity: Solar ultraviolet radiation affects the toxicity of natural and man-made chemicals

DOE Office of Scientific and Technical Information (OSTI.GOV)

Larson, R.A.; Berenbaum, M.R.

1988-04-01

Ultraviolet radiation appears to be toxic to all forms of unpigmented living cells, including bacteria, protozoa, nematodes, arthropods, fish, birds, and mammals. In addition to the direct absorption of solar energy by cellular constituents, toxicity may occur because of the absorption of sunlight by xenobiotics (or by naturally occurring compounds outside the target cell); these may be converted by light or by subsequent light-promoted reactions that induce cellular damage. This article describes the phototoxicity of photodynamic dyes, light-activated synthetic herbicides, petroleum and its constituents, and naturally occurring chemicals from plants. Detoxification mechanisms are also discussed.

Observations of the peculiar object MWC 560 in outburst

NASA Technical Reports Server (NTRS)

Michalitsianos, A. G.; Maran, S. P.; Oliversen, R. J.; Bopp, B.; Kontizas, E.

1991-01-01

The results of ultraviolet spectroscopy, photoelectric photometry, and supplemental high-resolution H(alpha) spectroscopy of a photometric outburst of MWC 560 are discussed. Ultraviolet spectra are shown to be consistent with the ejection of an optically thick shell that produced strong absorption blends of Fe II and Cr II. The velocities reported exceed by far those previously found in symbiotic stars or recurrent novas. In addition to the variable high-velocity system of broad absorption features, a relatively stable system of Mg II, Mg I, Fe II, Cr II, and other ionic absorptions is observed. It is pointed out that the spectroscopic phenomena in MWC 560 resemble those found in XX Ophiuchi, but the velocities in the MWC 560 are an order of magnitude higher than those found in XX Oph.

Concentrations and characteristics of organic carbon in surface water in Arizona: Influence of urbanization

USGS Publications Warehouse

Westerhoff, P.; Anning, D.

2000-01-01

Dissolved (DOC) and total (TOC) organic carbon concentrations and compositions were studied for several river systems in Arizona, USA. DOC composition was characterized by ultraviolet and visible absorption and fluorescence emission (excitation wavelength of 370 nm) spectra characteristics. Ephemeral sites had the highest DOC concentrations, and unregulated perennial sites had lower concentrations than unregulated intermittent sites, regulated sites, and sites downstream from wastewater-treatment plants (p < 0.05). Reservoir outflows and wastewater-treatment plant effluent were higher in DOC concentration (p < 0.05) and exhibited less variability in concentration than inflows to the reservoirs. Specific ultraviolet absorbance values at 254 nm were typically less than 2 m-1(milligram DOC per liter)-1 and lower than values found in most temperate-region rivers, but specific ultraviolet absorbance values increased during runoff events. Fluorescence measurements indicated that DOC in desert streams typically exhibit characteristics of autochthonous sources; however, DOC in unregulated upland rivers and desert streams experienced sudden shifts from autochthonous to allochthonous sources during runoff events. The urban water system (reservoir systems and wastewater-treatment plants) was found to affect temporal variability in DOC concentration and composition. (C) 2000 Elsevier Science B.V.Dissolved (DOC) and total (TOC) organic carbon concentrations and compositions were studied for several river systems in Arizona, USA. DOC composition was characterized by ultraviolet and visible absorption and fluorescence emission (excitation wavelength of 370 nm) spectra characteristics. Ephemeral sites had the highest DOC concentrations, and unregulated perennial sites had lower concentrations than unregulated intermittent sites, regulated sites, and sites downstream from wastewater-treatment plants (p<0.05). Reservoir outflows and wastewater-treatment plant effluent were higher in DOC concentration (p<0.05) and exhibited less variability in concentration than inflows to the reservoirs. Specific ultraviolet absorbance values at 254 nm were typically less than 2 m-1(milligram DOC per liter)-1 and lower than values found in most temperate-region rivers, but specific ultraviolet absorbance values increased during runoff events. Fluorescence measurements indicated that DOC in desert streams typically exhibit characteristics of autochthonous sources; however, DOC in unregulated upland rivers and desert streams experienced sudden shifts from autochthonous to allochthonous sources during runoff events. The urban water system (reservoir systems and wastewater-treatment plants) was found to affect temporal variability in DOC concentration and composition.The influence of urbanization, becoming increasingly common in arid regions, on dissolved organic carbon (DOC) concentrations in surface water resources was studied. DOC concentration and composition, seasonal watershed runoff events, streamflow variations, water management practices, and urban infrastructure in several Arizona watersheds were monitored. Ephemeral sites had the highest DOC levels, and unregulated perennial sites and lower concentrations than unregulated intermittent sites, regulated sites, and sites downstream from wastewater treatment plants. Reservoir outflows and wastewater treatment plant effluent had higher and less variable DOC concentrations than inflows to reservoirs. UV absorbance values, fluorescence measurements, and other indicators suggest that urban water systems (reservoirs and wastewater treatment plants) affect temporal variability in DOC concentration and composition.

Effects of ultraviolet radiation, visible light, and infrared radiation on erythema and pigmentation: a review.

PubMed

Sklar, Lindsay R; Almutawa, Fahad; Lim, Henry W; Hamzavi, Iltefat

2013-01-01

The effects of ultraviolet radiation, visible light, and infrared radiation on cutaneous erythema, immediate pigment darkening, persistent pigment darkening, and delayed tanning are affected by a variety of factors. Some of these factors include the depth of cutaneous penetration of the specific wavelength, the individual skin type, and the absorption spectra of the different chromophores in the skin. UVB is an effective spectrum to induce erythema, which is followed by delayed tanning. UVA induces immediate pigment darkening, persistent pigment darkening, and delayed tanning. At high doses, UVA (primarily UVA2) can also induce erythema in individuals with skin types I-II. Visible light has been shown to induce erythema and a tanning response in dark skin, but not in fair skinned individuals. Infrared radiation produces erythema, which is probably a thermal effect. In this article we reviewed the available literature on the effects of ultraviolet radiation, visible light, and infrared radiation on the skin in regards to erythema and pigmentation. Much remains to be learned on the cutaneous effects of visible light and infrared radiation.

Far-ultraviolet spectral changes of titanium dioxide with gold nanoparticles by ultraviolet and visible light.

PubMed

Tanabe, Ichiro; Kurawaki, Yuji

2018-05-15

Attenuated total reflectance spectra including the far-ultraviolet (FUV, ≤200nm) region of titanium dioxide (TiO 2 ) with and without gold (Au) nanoparticles were measured. A newly developed external light-irradiation system enabled to observe spectral changes of TiO 2 with Au nanoparticles upon light irradiations. Absorption in the FUV region decreased and increased by the irradiation with ultraviolet and visible light, respectively. These spectral changes may reflect photo-induced electron transfer from TiO 2 to Au nanoparticles under ultraviolet light and from Au nanoparticles to TiO 2 under visible light, respectively. Copyright © 2017 Elsevier B.V. All rights reserved.

Far-ultraviolet Spectroscopy of the Nova-like Variable KQ Monocerotis: A New SW Sextantis Star?

NASA Astrophysics Data System (ADS)

Wolfe, Aaron; Sion, Edward M.; Bond, Howard E.

2013-06-01

New optical spectra obtained with the SMARTS 1.5 m telescope and archival International Ultraviolet Explorer (IUE) far-ultraviolet (FUV) spectra of the nova-like variable KQ Mon are discussed. The optical spectra reveal Balmer lines in absorption as well as He I absorption superposed on a blue continuum. The 2011 optical spectrum is similar to the KPNO 2.1 m IIDS spectrum we obtained 33 years earlier except that the Balmer and He I absorption is stronger in 2011. Far-ultraviolet IUE spectra reveal deep absorption lines due to C II, Si III, Si IV, C IV, and He II, but no P Cygni profiles indicative of wind outflow. We present the results of the first synthetic spectral analysis of the IUE archival spectra of KQ Mon with realistic optically thick, steady-state, viscous accretion-disk models with vertical structure and high-gravity photosphere models. We find that the photosphere of the white dwarf (WD) contributes very little FUV flux to the spectrum and is overwhelmed by the accretion light of a steady disk. Disk models corresponding to a WD mass of ~0.6 M ⊙, with an accretion rate of order 10-9 M ⊙ yr-1 and disk inclinations between 60° and 75°, yield distances from the normalization in the range of 144-165 pc. KQ Mon is discussed with respect to other nova-like variables. Its spectroscopic similarity to the FUV spectra of three definite SW Sex stars suggests that it is likely a member of the SW Sex class and lends support to the possibility that the WD is magnetic.

Inference of a 7.75 eV lower limit in the ultraviolet pumping of interstellar polycyclic aromatic hydrocarbon cations with resulting unidentified infrared emissions

NASA Technical Reports Server (NTRS)

Robinson, M. S.; Beegle, L. W.; Wdowiak, T. J.

1997-01-01

The discrete infrared features known as the unidentified infrared (UIR) bands originating in starburst regions of other galaxies, and in H II regions and planetary nebulae within the Milky Way, are widely thought to be the result of ultraviolet pumped infrared fluorescence of polycyclic aromatic hydrocarbon (PAH) molecules and ions. These UIR emissions are estimated to account for 10%-30% of the total energy emitted by galaxies. Laboratory absorption spectra including the vacuum ultraviolet region, as described in this paper, show a weakening of the intensity of absorption features as the population of cations increases, suggesting that strong pi* <-- pi transitions are absent in the spectra of PAH cations. This implies a lower energy bound for ultraviolet photons that pump infrared emissions from such ions at 7.75 eV, an amount greater than previously thought. The implications include size and structure limitations on the PAH molecules and ions which are apparent constituents of the interstellar medium. Also, this might affect estimations of the population of early-type stars in regions of rapid star formation.

Quantum state engineering with ultra-short-period (AlN)m/(GaN)n superlattices for narrowband deep-ultraviolet detection.

PubMed

Gao, Na; Lin, Wei; Chen, Xue; Huang, Kai; Li, Shuping; Li, Jinchai; Chen, Hangyang; Yang, Xu; Ji, Li; Yu, Edward T; Kang, Junyong

2014-12-21

Ultra-short-period (AlN)m/(GaN)n superlattices with tunable well and barrier atomic layer numbers were grown by metal-organic vapour phase epitaxy, and employed to demonstrate narrowband deep ultraviolet photodetection. High-resolution transmission electron microscopy and X-ray reciprocal space mapping confirm that superlattices containing well-defined, coherently strained GaN and AlN layers as thin as two atomic layers (∼ 0.5 nm) were grown. Theoretical and experimental results demonstrate that an optical absorption band as narrow as 9 nm (210 meV) at deep-ultraviolet wavelengths can be produced, and is attributable to interband transitions between quantum states along the [0001] direction in ultrathin GaN atomic layers isolated by AlN barriers. The absorption wavelength can be precisely engineered by adjusting the thickness of the GaN atomic layers because of the quantum confinement effect. These results represent a major advance towards the realization of wavelength selectable and narrowband photodetectors in the deep-ultraviolet region without any additional optical filters.

Solar absorptance and thermal emittance of some common spacecraft thermal-control coatings

NASA Technical Reports Server (NTRS)

Henninger, J. H.

1984-01-01

Solar absorptance and thermal emittance of spacecraft materials are critical parameters in determining spacecraft temperature control. Because thickness, surface preparation, coatings formulation, manufacturing techniques, etc. affect these parameters, it is usually necessary to measure the absorptance and emittance of materials before they are used. Absorptance and emittance data for many common types of thermal control coatings, are together with some sample spectral data curves of absorptance. In some cases for which ultraviolet and particle radiation data are available, the degraded absorptance and emittance values are also listed.

The role of film interfaces in near-ultraviolet absorption and pulsed-laser damage in ion-beam-sputtered coatings based on HfO 2/SiO 2 thin-film pairs

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ristau, Detlev; Papernov, S.; Kozlov, A. A.

2015-11-23

The role of thin-film interfaces in the near-ultraviolet absorption and pulsed-laser–induced damage was studied for ion-beam–sputtered and electron-beam–evaporated coatings comprised from HfO 2 and SiO 2 thin-film pairs. To separate contributions from the bulk of the film and from interfacial areas, absorption and damage-threshold measurements were performed for a one-wave (355-nm wavelength) thick, HfO 2 single-layer film and for a film containing seven narrow HfO 2 layers separated by SiO 2 layers. The seven-layer film was designed to have a total optical thickness of HfO 2 layers, equal to one wave at 355 nm and an E-field peak and averagemore » intensity similar to a single-layer HfO 2 film. Absorption in both types of films was measured using laser calorimetry and photothermal heterodyne imaging. The results showed a small contribution to total absorption from thin-film interfaces, as compared to HfO 2 film material. The relevance of obtained absorption data to coating near-ultraviolet, nanosecond-pulse laser damage was verified by measuring the damage threshold and characterizing damage morphology. The results of this study revealed a higher damage resistance in the seven-layer coating as compared to the single-layer HfO 2 film in both sputtered and evaporated coatings. Here, the results are explained through the similarity of interfacial film structure with structure formed during the co-deposition of HfO 2 and SiO 2 materials.« less

Spectrophotometer-Integrating-Sphere System for Computing Solar Absorptance

NASA Technical Reports Server (NTRS)

Witte, William G., Jr.; Slemp, Wayne S.; Perry, John E., Jr.

1991-01-01

A commercially available ultraviolet, visible, near-infrared spectrophotometer was modified to utilize an 8-inch-diameter modified Edwards-type integrated sphere. Software was written so that the reflectance spectra could be used to obtain solar absorptance values of 1-inch-diameter specimens. A descriptions of the system, spectral reflectance, and software for calculation of solar absorptance from reflectance data are presented.

Ultraviolet spectroscopic breath analysis using hollow-optical fiber as gas cell

NASA Astrophysics Data System (ADS)

Iwata, T.; Katagiri, T.; Matsuura, Y.

2017-02-01

For breath analysis on ultraviolet absorption spectroscopy, an analysis system using a hollow optical fiber as gas cell is developed. The hollow optical fiber functions as a long path and extremely small volume gas cell. Firstly, the measurement sensitivity of the system is evaluated by using NO gas as a gas sample. The result shows that NO gas with 50 ppb concentration is measured by using a system with a laser-driven, high intensity light source and a 3-meter long, aluminum-coated hollow optical fiber. Then an absorption spectrum of breath sample is measured in the wavelength region of around 200-300 nm and from the spectrum, it is found that the main absorbing components in breath were H2O, isoprene, and O3 converted from O2 by radiation of ultraviolet light. Then the concentration of isoprene in breath is estimated by using multiple linear regression analysis.

Direct index of refraction measurements at extreme-ultraviolet and soft-x-ray wavelengths.

PubMed

Rosfjord, Kristine; Chang, Chang; Miyakawa, Ryan; Barth, Holly; Attwood, David

2006-03-10

Coherent radiation from undulator beamlines has been used to directly measure the real and imaginary parts of the index of refraction of several materials at both extreme-ultraviolet and soft-x-ray wavelengths. Using the XOR interferometer, we measure the refractive indices of silicon and ruthenium, essential materials for extreme-ultraviolet lithography. Both materials are tested at wavelength (13.4 nm) and across silicon's L2 (99.8 eV) and L3 (99.2 eV) absorption edges. We further extend this direct phase measurement method into the soft-x-ray region, where measurements of chromium and vanadium are performed around their L3 absorption edges at 574.1 and 512.1 eV, respectively. These are the first direct measurements, to our knowledge, of the real part of the index of refraction made in the soft-x-ray region.

Stabilization and enhanced energy gap by Mg doping in ɛ-phase Ga2O3 thin films

NASA Astrophysics Data System (ADS)

Bi, Xiaoyu; Wu, Zhenping; Huang, Yuanqi; Tang, Weihua

2018-02-01

Mg-doped Ga2O3 thin films with different doping concentrations were deposited on sapphire substrates using laser molecular beam epitaxy (L-MBE) technique. X-ray diffraction (XRD), x-ray photoelectron spectroscopy (XPS) and ultraviolet-visible (UV-vis) absorption spectrum were used to characterize the crystal structure and optical properties of the as-grown films. Compared to pure Ga2O3 thin film, the Mg-doped thin films have transformed from the most stable β-phase into ɛ-phase. The absorption edge shifted to about 205 nm and the optical bandgap increased to ˜ 6 eV. These properties reveal that Mg-doped Ga2O3 films may have potential applications in the field of deep ultraviolet optoelectronic devices, such as deep ultraviolet photodetectors, short wavelength light emitting devices and so on.

Chromophores in human skin

NASA Astrophysics Data System (ADS)

Young, Antony R.

1997-05-01

Human skin, especially the epidermis, contains several major solar ultraviolet-radiation- (UVR-) absorbing endogenous chromophores including DNA, urocanic acid, amino acids, melanins and their precursors and metabolites. The lack of solubility of melanins prevents their absorption spectra being defined by routine techniques. Indirect spectroscopic methods show that their spectral properties depend on the stimulus for melanogenesis. The photochemical consequences of UVR absorption by some epidermal chromophores are relatively well understood whereas we lack a detailed understanding of the consequent photobiological and clinical responses. Skin action spectroscopy is not a reliable way of relating a photobiological outcome to a specific chromophore but is important for UVR hazard assessment. Exogenous chromophores may be administered to the skin in combination with UVR exposure for therapeutic benefit, or as sunscreens for the prevention of sunburn and possibly skin cancer.

Discovery of an Ultraviolet Counterpart to an Ultrafast X-Ray Outflow in the Quasar PG 1211+143

NASA Astrophysics Data System (ADS)

Kriss, Gerard A.; Lee, Julia C.; Danehkar, Ashkbiz; Nowak, Michael A.; Fang, Taotao; Hardcastle, Martin J.; Neilsen, Joseph; Young, Andrew

2018-02-01

We observed the quasar PG 1211+143 using the Cosmic Origins Spectrograph on the Hubble Space Telescope in 2015 April as part of a joint campaign with the Chandra X-ray Observatory and the Jansky Very Large Array. Our ultraviolet spectra cover the wavelength range 912–2100 Å. We find a broad absorption feature (∼ 1080 {km} {{{s}}}-1) at an observed wavelength of 1240 Å. Interpreting this as H I Lyα, in the rest frame of PG 1211+143 (z = 0.0809), this corresponds to an outflow velocity of ‑16,980 {km} {{{s}}}-1 (outflow redshift {z}{out}∼ -0.0551), matching the moderate ionization X-ray absorption system detected in our Chandra observation and reported previously by Pounds et al. With a minimum H I column density of {log} {N}{{H}{{I}}}> 14.5, and no absorption in other UV resonance lines, this Lyα absorber is consistent with arising in the same ultrafast outflow as the X-ray absorbing gas. The Lyα feature is weak or absent in archival ultraviolet spectra of PG 1211+143, strongly suggesting that this absorption is transient, and intrinsic to PG 1211+143. Such a simultaneous detection in two independent wavebands for the first time gives strong confirmation of the reality of an ultrafast outflow in an active galactic nucleus.

Pluto's Far Ultraviolet Spectrum and Airglow Emissions

NASA Astrophysics Data System (ADS)

Steffl, A.; Schindhelm, E.; Kammer, J.; Gladstone, R.; Greathouse, T. K.; Parker, J. W.; Strobel, D. F.; Summers, M. E.; Versteeg, M. H.; Ennico Smith, K.; Hinson, D. P.; Linscott, I.; Olkin, C.; Parker, A. H.; Retherford, K. D.; Singer, K. N.; Tsang, C.; Tyler, G. L.; Weaver, H. A., Jr.; Woods, W. W.; Young, L. A.; Stern, A.

2015-12-01

The Alice far ultraviolet spectrograph on the New Horizons spacecraft is the second in a family of six instruments in flight on, or under development for, NASA and ESA missions. Here, we present initial results from the Alice observations of Pluto during the historic flyby. Pluto's far ultraviolet spectrum is dominated by sunlight reflected from the surface with absorption by atmospehric constituents. We tentatively identify C2H2 and C2H4 in Pluto's atmosphere. We also present evidence for weak airglow emissions.

Observations of the Ultraviolet Spectra of Helium (DB) White Dwarfs and a Study of the Ultraviolet Spectra of White Dwarfs Containing Carbon

NASA Technical Reports Server (NTRS)

Wegner, G. A.

1984-01-01

Strong ultraviolet carbon lines were detected in the spectrum of the southern DC white dwarf BPM 11668. Observations of a number of hotter DB white dwarfs with IUE show no evidence of carbon features. Two additional DA white dwarfs were observed that have the strong unidentified absorption near 1400 A which now seems to be identified with another lower temperature feature as satellite lines to Lyman alpha radiation.

Interstellar absorption of the extreme ultraviolet flux from two hot white dwarfs

NASA Technical Reports Server (NTRS)

Cash, W.; Bowyer, S.; Lampton, M.

1979-01-01

Photometric upper limits on the 300 A flux from the hot white dwarfs Feige 24 and G191-B2B are presented. The limits, which were obtained with a rocket-borne extreme ultraviolet imaging telescope, are interpreted as lower limits on the density of the intervening interstellar matter. The limits are used to investigate the state of interstellar gas within 100 pc. A local clumpiness factor, which is of value in planning future extreme ultraviolet observations, is derived.

A refractory metamaterial absorber for ultra-broadband, omnidirectional and polarization-independent absorption in the UV-NIR spectrum.

PubMed

Huang, Yijia; Liu, Ling; Pu, Mingbo; Li, Xiong; Ma, Xiaoliang; Luo, Xiangang

2018-05-03

In this paper, efficient ultra-broadband absorption from ultraviolet (UV) to near infrared (NIR) is achieved using a metamaterial perfect absorber (MPA) with refractory constituents. Both simulated and experimental results indicate that this proposed MPA exhibits an average absorption over 95% at wavelengths ranging from 200 nm to 900 nm. Besides, owing to the ultrathin thickness and symmetrical topology of this device, it exhibits great angular tolerance up to 60° independent of the incident polarizations. Excellent thermal stability is also demonstrated at high operation temperatures. The physical origin of the ultra-broadband characteristics is mainly based on diffraction/interference engineering at short wavelengths and the anti-reflection effect at long wavelengths. We believe that such a device may find potential applications ranging from photodetection and photothermal energy conversion to ultraviolet protection and thermophotovoltaics.

Ultraviolet absorption experiment MA-059

NASA Technical Reports Server (NTRS)

Donahue, T. M.; Hudson, R. D.; Anderson, J.; Kaufman, F.; Mcelroy, M. B.

1976-01-01

The ultraviolet absorption experiment performed during the Apollo Soyuz mission involved sending a beam of atomic oxygen and atomic nitrogen resonance radiation, strong unabsorbable oxygen and nitrogen radiation, and visual radiation, all filling the same 3 deg-wide field of view from the Apollo to the Soyuz. The radiation struck a retroreflector array on the Soyuz and was returned to a spectrometer onboard the Apollo. The density of atomic oxygen and atomic nitrogen between the two spacecraft was measured by observing the amount of resonance radiation absorbed when the line joining Apollo and Soyuz was perpendicular to their velocity with respect to the ambient atmosphere. Information concerning oxygen densities was also obtained by observation of resonantly fluorescent light. The absorption experiments for atomic oxygen and atomic nitrogen were successfully performed at a range of 500 meters, and abundant resonance fluorescence data were obtained.

Real-Time Analysis of Isoprene in Breath by Using Ultraviolet-Absorption Spectroscopy with a Hollow Optical Fiber Gas Cell

PubMed Central

Iwata, Takuro; Katagiri, Takashi; Matsuura, Yuji

2016-01-01

A breath analysis system based on ultraviolet-absorption spectroscopy was developed by using a hollow optical fiber as a gas cell for real-time monitoring of isoprene in breath. The hollow optical fiber functions as an ultra-small-volume gas cell with a long path. The measurement sensitivity of the system was evaluated by using nitric-oxide gas as a gas sample. The evaluation result showed that the developed system, using a laser-driven, high-intensity light source and a 3-m-long, aluminum-coated hollow optical fiber, could successfully measure nitric-oxide gas with a 50 ppb concentration. An absorption spectrum of a breath sample in the wavelength region of around 200–300 nm was measured, and the measured spectrum revealed the main absorbing components in breath as water vapor, isoprene, and ozone converted from oxygen by radiation of ultraviolet light. The concentration of isoprene in breath was estimated by multiple linear regression. The regression analysis results showed that the proposed analysis system enables real-time monitoring of isoprene during the exhaling of breath. Accordingly, it is suitable for measuring the circadian variation of isoprene. PMID:27929387

Mass loss in the interacting semi-detached binary delta librae

NASA Technical Reports Server (NTRS)

Mccluskey, George E., Jr.; Mccluskey, Carolina P. S.; Kondo, Yoji

1995-01-01

The interacting Algol-type binary Delta Librae (AOV + G: V) has been observed with the International Ultraviolet Explorer (IUE) satellite. More than fifty high resolution spectra in the far-ultraviolet and mid-ultraviolet spectrum have been analyzed in order to model the mass flow in the Delta Librae system. The resonance lines of Si IV and C IV are present in absorption and vary in strength both secularly and with phase. The radial velocities of the Si IV and C IV absorption lines generally follow the orbital motion of the primary star but deviate by typically a few tens of kilometers per second in the direction of the observer. The presence of Si IV and C IV features indicates the existence of a region considerably hotter than the normal AOV photosphere and, since these lines are present at all phases, this region must be fairly extensive. These results are interpreted in terms of a 'pseudo-photosphere' around the equatorial region of the AOV star, created by matter being accreted from the G-type companion. The widths of the Si IV and C IV absorption features imply that some of the matter lost by the G-star leaves the system entirely.

Two-phase ultraviolet spectrophotometry of the pulsating white dwarf ZZ Piscium

NASA Technical Reports Server (NTRS)

Bond, H. E.; Kemper, E.; Grauer, A. D.; Holm, A. V.; Panek, R. J.; Schiffer, F. H., III

1985-01-01

Spectra of the pulsating white dwarf ZZ Psc (= G29-38) were obtained using the International Ultraviolet Explorer. By using a multiple-exposure technique in conjunction with simultaneous ground-based exposure-metering photometry, it was possible to obtain mean on-pulse and off-pulse spectra in the 1950-1310 A wavelength range. The ratio of the time-averaged on-pulse to off-pulse spectra is best fitted by a temperature variation that is in phase with the optical light variation. This result is consistent with the hypothesis that the observed variation is due to a high-order nonradial pulsation. Conventional ultraviolet spectra of ZZ Psc showed broad absorption features at 1390 and 1600 A. These features are also found in the spectra of the cool DA-type white dwarfs G226-29 and G67-23, and appear to increase in strength with decreasing temperature. A possible explanation for the 1600 A feature is absorption by the satellite band of resonance-broadened hydrogen Ly-alpha. Such absorption would also help explain a discrepancy between the observed pulsation amplitude shortward of 1650 A and the predicted amplitudes based on model atmospheres.

Real-Time Analysis of Isoprene in Breath by Using Ultraviolet-Absorption Spectroscopy with a Hollow Optical Fiber Gas Cell.

PubMed

Iwata, Takuro; Katagiri, Takashi; Matsuura, Yuji

2016-12-05

A breath analysis system based on ultraviolet-absorption spectroscopy was developed by using a hollow optical fiber as a gas cell for real-time monitoring of isoprene in breath. The hollow optical fiber functions as an ultra-small-volume gas cell with a long path. The measurement sensitivity of the system was evaluated by using nitric-oxide gas as a gas sample. The evaluation result showed that the developed system, using a laser-driven, high-intensity light source and a 3-m-long, aluminum-coated hollow optical fiber, could successfully measure nitric-oxide gas with a 50 ppb concentration. An absorption spectrum of a breath sample in the wavelength region of around 200-300 nm was measured, and the measured spectrum revealed the main absorbing components in breath as water vapor, isoprene, and ozone converted from oxygen by radiation of ultraviolet light. The concentration of isoprene in breath was estimated by multiple linear regression. The regression analysis results showed that the proposed analysis system enables real-time monitoring of isoprene during the exhaling of breath. Accordingly, it is suitable for measuring the circadian variation of isoprene.

Laboratory Measurements of SO2 and N2 Absorption Spectra for Planetary Atmospheres

NASA Technical Reports Server (NTRS)

Stark, Glenn

2003-01-01

This laboratory project focuses on the following topics: 1) Measurement of SO2 ultraviolet absorption cross sections; and 2) N2 band and Line Oscillator Strengths and Line Widths in the 80 to 100 nm region. Accomplishments for these projects are summarized.

Altmetric: 165More detailArticle | OPENClimate change-induced increases in precipitation are reducing the potential for solar ultraviolet radiation to inactivate pathogens in surface waters

EPA Science Inventory

Climate change is accelerating the release of dissolved organic matter (DOM) to inland and coastal waters through increases in precipitation, thawing of permafrost, and changes in vegetation. Our modeling approach suggests that the selective absorption of ultraviolet radiation (U...

Phyllosphere Methylobacterium bacteria contain UVA-absorbing compounds.

PubMed

Yoshida, Shigenobu; Hiradate, Syuntaro; Koitabashi, Motoo; Kamo, Tsunashi; Tsushima, Seiya

2017-02-01

Microbes inhabiting the phyllosphere encounter harmful ultraviolet rays, and must develop adaptive strategies against this irradiation. In this study, we screened bacterial isolates originating from the phyllosphere of various plants which harbored absorbers of ultraviolet A (UVA), a wavelength range which is recognized as harmful to human skin. Of the 200 phyllosphere bacterial isolates we screened, methanol extracts from bacterial cells of seventeen isolates absorbed wavelengths in the range of 315-400nm. All of the UVA-absorbing strains belonged to Methylobacterium species based on 16S ribosomal RNA gene sequences, suggesting that cells of this bacterial genus contain specific UVA-absorbing compounds. When cells of a representative Methylobacterium strain were extracted using various solvents, UVA absorption was observed in the extracts obtained using several aqueous solvents, indicating that the UVA-absorbing compounds were highly polar. A compound was purified using solid columns and HPLC separation, and comparative analysis revealed that the absorption strength and spectrum of the compound were similar to those of the known UVA filter, avobenzone. The compound was also verified to be stable under UVA exposure for at least 480min. Based on these results, the UVA-absorbing compound harbored by Methylobacterium has potential to be used as a novel sunscreen ingredient. Copyright © 2016 Elsevier B.V. All rights reserved.

Synchrotron Photoionization Mass Spectrometry Measurements of Kinetics and Product Formation in the Allyl Radical (H2CCHCH2)Self Reaction

NASA Technical Reports Server (NTRS)

Selby, Talitha M.; Melini, giovanni; Goulay, Fabien; Leone, Stephen R.; Fahr, Askar; Taatjes, Craig A.; Osborn, David L.

2008-01-01

Product channels for the self-reaction of the resonance-stabilized allyl radical, C3H5 + C3H5, have been studied with isomeric specificity at temperatures from 300-600 K and pressures from 1-6 Torr using time-resolved multiplexed photoionization mass spectrometry. Under these conditions 1,5-hexadiene was the only C6H10 product isomer detected. The lack of isomerization of the C6H10 product is in marked contrast to the C6H6 product in the related C3H3 + C3H3 reaction, and is due to the more saturated electronic structure of the C6H10 system. The disproportionation product channel, yielding allene + propene, was also detected, with an upper limit on the branching fraction relative to recombination of 0.03. Analysis of the allyl radical decay at 298 K yielded a total rate coefficient of (2.7 +/- 0.8) x 10(exp -11) cu cm/molecule/s, in good agreement with pre.vious experimental measurements using ultraviolet kinetic absorption spectroscopy and a recent theoretical determination using variable reaction coordinate transition state theory. This result provides independent indirect support for the literature value of the allyl radical ultraviolet absorption cross-section near 223 nm.

Biochemical Detection and Identification False Alarm Rate Dependence on Wavelength Using Laser Induced Fluorescence

NASA Technical Reports Server (NTRS)

Bhartia, R.; Hug, W. F.; Sala, E. C.; Sijapati, K.; Lane, A. L.; Reid, R. D.; Conrad, P. G.

2006-01-01

Most organic and many inorganic materials absorb strongly in specific wavelength ranges in the deep UV between about 220nm and 300nm. Excitation within these absorption bands results in native fluorescence emission. Each compound or composite material, such as a bacterial spore, has a unique excitation-emission fingerprint that can be used to provide information about the material. The sensitivity and specificity with which these materials can be detected and identified depends on the excitation wavelength and the number and location of observation wavelengths.We will present data on our deep ultraviolet Targeted Ultraviolet Chemical Sensors that demonstrate the sensitivity and specificity of the sensors. In particular, we will demonstrate the ability to quantitatively differentiate a wide range of biochemical agent targets against a wide range of background materials. We will describe the relationship between spectral resolution and specificity in target identification, as well as simple, fast, algorithms to identify materials.Hand-held, battery operated instruments using a deep UV laser and multi-band detection have been developed and deployed on missions to the Antarctic, the Arctic, and the deep ocean with the capability of detecting a single bacterial spore and to differentiate a wide range of organic and biological compounds.

[Effect of Charge-Transfer Complex on Ultraviolet-Visible (UV-Vis) Absorption Property of Chromophoric Dissolved Organic Matter (CDOM) in Waters of Typical Water-Level Fluctuation Zones of the Three Gorges Reservoir Areas].

PubMed

Jiang, Tao; Liang, Jian; Zhang, Mu-xue; Wang, Ding-yong; Wei, Shi-qiang; Lu, Song

2016-02-15

As an important fraction of dissolved organic matter (DOM), chromophoric dissolved organic matter (CDOM) plays a key role in decision of the optical properties and photogeochemistry of DOM, and further affects pollutant fate and global carbon cycle. These optical properties are ascribed to two chromophoric systems including superposition of individual chromophores and charge-transfer (CT) complexation between electron donor (e.g., phenols and indoles) and acceptor (e.g., quinones and other oxidized aromatics) in DOM structures. Thus in this study, based on the "double-chromophoric system" model, DOM samples from four typical water-level fluctuation zones of Three Gorges Reservoir (TGR) areas were selected, to investigate the effect and contribution of charge-transfer complex to ultraviolet-visible (UV-Vis) absorption property of CDOM. Using NaBH, reduction method, original featureless absorption curve was classified into two independent curves caused by individual chromophoric group, which were derived from a simple superposition of independent chromophore and charge-transfer complex, respectively. Also, the changes in curve properties and specific parameters before and after NaBH4 reduction were compared. The results showed that in all DOM samples from the four sites of TGR, more than 35% of absorption was attributed from CT complex. Shibaozhai of Zhongxian and Zhenxi of Fuling showed the highest proportion ( > 50%). It suggested that the role of CT complex in CDOM property could not be neglected. After removal of CT complex, absorption curve showed blue-shift and CDOM concentration [a (355)] decreased significantly. Meanwhile, because of deforming of bonds by reduction, DOM structures became more dispersive and the molecular size was decreased, resulting in the lower spectral slope (S) observed, which evidentially supported that the supermolecular association structure of DOM was self-assembled through CT complex. Meanwhile, deceasing hydrophobic components led to decreased apparent aromaticity (lower SUVA values), whereas specific parameters including SUVA, CDOM and SR still were applicable for comparison among different DOM samples instead of the same sample without consideration of "double-cbromopboric system" model involving tbe role of CT complex. Comparatively, S(275-295) was dynamic due to tbe impact of CT effect. Furtbermore, establisbing DOC estimation model by short-wavelength range of CDOM was recommended because of its stability despite of CT complex.

Laboratory measurements and modeling of molecular photoabsorption in the ultraviolet for planetary atmospheres applications: diatomic sulfur and sulfur monoxide

NASA Astrophysics Data System (ADS)

Stark, Glenn

2016-07-01

Our research program comprises the measurement and modeling of ultraviolet molecular photoabsorption cross sections with the highest practical resolution. It supports efforts to interpret and model observations of planetary atmospheres. Measurement and modeling efforts on diatomic sulfur (S _{2}) and sulfur monoxide (SO) are in progress. S _{2}: Interpretations of atmospheric (Io, Jupiter, cometary comae) S _{2} absorption features are hindered by a complete lack of laboratory cross section data in the ultraviolet. We are working to quantify the photoabsorption spectrum of S _{2} from 240 to 300 nm based on laboratory measurements and theoretical calculations. We have constructed an experimental apparatus to produce a stable column of S _{2} vapor at a temperature of 800 K. High-resolution measurements of the absorption spectrum of the strong B - X system of S _{2} were completed using the NIST VUV-FTS at Gaithersburg, Maryland. These measurements are currently being incorporated into a coupled-channel model of the absorption spectrum of S _{2} to quantify the contributions from individual band features and to establish the mechanisms responsible for the strong predissociation signature of the B - X system. A successful coupled channels model can then be used to calculate the B - X absorption spectrum at any temperature. SO: There has been a long-standing need for high-resolution cross sections of sulfur monoxide radicals in the ultraviolet and vacuum ultraviolet regions, where the molecule strongly predissociates, for modeling the atmospheres of Io and Venus, and most recently for understanding sulfur isotope effects in the ancient (pre-O _{2}) atmosphere of Earth. We have produced a measurable column of SO in a continuous-flow DC discharge cell, using SO _{2} as a parent molecule. Photoabsorption measurements were recently recorded on the DESIRS beamline of the SOLEIL synchrotron, taking advantage of the high-resolution VUV-FTS on that beamline. A number of strong, predissociated SO bands were measured in the 140 to 200 nm region. Weaker features associated with the SO B - X system were simultaneously recorded, allowing for an approximate determination of the VUV SO band f-values.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Marron, A.C.

Middle ultraviolet spectra of the atmospheric airglow were obtained from a March 1992 rocket flight of the NPS MUSTANG instrument. These spectra are analyzed from 1900 A to 3100 A, over an altitude range of 100 km to 320 km. The data are modeled with computer generated synthetic spectra for the following emissions: N2 Vegard Kaplan (VK); N2 Lyman-Birge-Hopfield (LBH); and NO Gamma, Delta, and Epsilon bands. A best fit procedure was developed. The resulting synthetic spectra agree well with obtained airglow data. Confirmation was made of the theoretical self absorption versus non-self absorption processes of the NO (0,0), (1,0),more » (2,0) gamma resonance band emissions. NO self absorption is a necessary inclusion of any atmospheric nitric oxide analysis stratagem. Profiles of temperature versus altitude and NO column density versus altitude for the rocket flight are estimated. Airglow, Ionosphere, Ultraviolet spectroscopy.« less

Ultraviolet absorption by highly ionized halo gas near the Galactic center

NASA Technical Reports Server (NTRS)

Savage, B. D.; Massa, D.

1985-01-01

Initial results are presented for a program to survey highly ionized gas in the Milky Way disk and halo. High-resolution IUE (International Ultraviolet Explorer) far-UV spectra were obtained for 12 stars at galactocentric distances less than 6 kpc. The stars are 0.7-2.2 kpc away from the plane. Most of the spectra contain exceedingly strong and broad interstellar absorption lines of weakly and highly ionized atoms. In addition to the normally strong lines of Si IV and C IV, strong interstellar NV lines have been detected in the spectra of eight stars. The detection of NV absorption (amounting to more than 10 times the predicted NV) provides an important new constraint on models for the origin of Galactic halo gas. A Galactic fountain operating in the presence of known UV and EUV radiation might explain the observations.

The Copernicus ultraviolet spectral atlas of Sirius

NASA Technical Reports Server (NTRS)

Rogerson, John B., Jr.

1987-01-01

A near-ultraviolet spectral atlas for the A1 V star Alpha CMa (Sirius) has been prepared from data taken by the Princeton spectrometer aboard the Copernicus satellite. The spectral region from 1649 to 3170 A has been scanned with a resolution of 0.1 A. The atlas is presented in graphs, and line identifications for the absorption features have been tabulated.

Detection of Ozone and Nitric Oxide in Decomposition Products of Air-Insulated Switchgear Using Ultraviolet Differential Optical Absorption Spectroscopy (UV-DOAS).

PubMed

Li, Yalong; Zhang, Xiaoxing; Li, Xin; Cui, Zhaolun; Xiao, Hai

2018-01-01

Air-insulated switchgear cabinets play a role in the protection and control of the modern power grid, and partial discharge (PD) switchgear is a long-term process in the non-normal operation of one of the situations; thus, condition monitoring of the switchgear is important. The air-insulated switchgear during PD enables the decomposition of air components, namely, O 3 and NO. A set of experimental platforms was designed on the basis of the principle of ultraviolet differential optical absorption spectroscopy (UV-DOAS) to detect O 3 and NO concentrations in air-insulated switchgear. Differential absorption algorithm and wavelet transform were used to extract effective absorption spectra; a linear relationship between O 3 and NO concentrations and absorption spectrum data were established. O 3 detection linearity was up to 0.9992 and the detection limit was at 3.76 ppm. NO detection linearity was up to 0.9990 and the detection limit was at 0.64 ppm. Results indicate that detection platform is suitable for detecting trace O 3 and NO gases produced by PD of the air-insulated switchgear.

Tunable UV-visible absorption of SnS2 layered quantum dots produced by liquid phase exfoliation.

PubMed

Fu, Xiao; Ilanchezhiyan, P; Mohan Kumar, G; Cho, Hak Dong; Zhang, Lei; Chan, A Sattar; Lee, Dong J; Panin, Gennady N; Kang, Tae Won

2017-02-02

4H-SnS 2 layered crystals synthesized by a hydrothermal method were used to obtain via liquid phase exfoliation quantum dots (QDs), consisting of a single layer (SLQDs) or multiple layers (MLQDs). Systematic downshift of the peaks in the Raman spectra of crystals with a decrease in size was observed. The bandgap of layered QDs, estimated by UV-visible absorption spectroscopy and the tunneling current measurements using graphene probes, increases from 2.25 eV to 3.50 eV with decreasing size. 2-4 nm SLQDs, which are transparent in the visible region, show selective absorption and photosensitivity at wavelengths in the ultraviolet region of the spectrum while larger MLQDs (5-90 nm) exhibit a broad band absorption in the visible spectral region and the photoresponse under white light. The results show that the layered quantum dots obtained by liquid phase exfoliation exhibit well-controlled and regulated bandgap absorption in a wide tunable wavelength range. These novel layered quantum dots prepared using an inexpensive method of exfoliation and deposition from solution onto various substrates at room temperature can be used to create highly efficient visible-blind ultraviolet photodetectors and multiple bandgap solar cells.

Probing the Southern Fermi Bubble in Ultraviolet Absorption Using Distant AGNs

NASA Astrophysics Data System (ADS)

Karim, Md Tanveer; Fox, Andrew J.; Jenkins, Edward B.; Bordoloi, Rongmon; Wakker, Bart P.; Savage, Blair D.; Lockman, Felix J.; Crawford, Steven M.; Jorgenson, Regina A.; Bland-Hawthorn, Joss

2018-06-01

The Fermi Bubbles are two giant gamma-ray emitting lobes extending 55° above and below the Galactic center. While the Northern Bubble has been extensively studied in ultraviolet (UV) absorption, little is known about the gas kinematics of the southern Bubble. We use UV absorption-line spectra from the Cosmic Origins Spectrograph (COS) on the Hubble Space Telescope to probe the southern Fermi Bubble using a sample of 17 background AGNs projected behind or near the Bubble. We measure the incidence of high-velocity clouds (HVC), finding that 4 out of 6 sightlines passing through the Bubble show HVC absorption, versus 6 out of 11 passing outside. We find strong evidence that the maximum absolute LSR velocity of the HVC components decreases as a function of galactic latitude within the Bubble, for both blueshifted and redshifted components, as expected for a decelerating outflow. We explore whether the column density ratios Si IV/Si III, Si IV/Si II, and Si III/Si II correlate with the absolute galactic latitude within the Bubble. These results demonstrate the use of UV absorption-line spectroscopy to characterize the kinematics and ionization conditions of embedded clouds in the Galactic center outflow.

The early faint sun paradox: organic shielding of ultraviolet-labile greenhouse gases

NASA Technical Reports Server (NTRS)

Sagan, C.; Chyba, C.

1997-01-01

Atmospheric mixing ratios of approximately 10(-5 +/- 1) for ammonia on the early Earth would have been sufficient, through the resulting greenhouse warming, to counteract the temperature effects of the faint early sun. One argument against such model atmospheres has been the short time scale for ammonia photodissociation by solar ultraviolet light. Here it is shown that ultraviolet absorption by steady-state amounts of high-altitude organic solids produced from methane photolysis may have shielded ammonia sufficiently that ammonia resupply rates were able to maintain surface temperatures above freezing.

Photolytic separation of isotopes in cryogenic solution

DOEpatents

Freund, S.M.; Maier, W.B. II; Holland, R.F.; Battie, W.H.

Separation of carbon isotopes by photolysis of CS/sub 2/ in cryogenic solutions of nitrogen, krypton and argon with 206 nm light from an iodine resonance lamp is reported. The spectral distributionn of the ultraviolet absorption depends on solvent. Thus, in liquid nitrogen the photolytic decomposition rate of /sup 13/CS/sub 2/ is greater than that of /sup 12/CS/sub 2/ (because the absorption of 206 nm radiation is greater for /sup 13/CS/sub 2/), whereas in liquid krypton and liquid argon the reverse is true. The shift in ultraviolet spectrum is a general phenomenon readily characterized as a function of solvent polarizability, and exhibits behavior similar to that for vibrational transitions occurring in the infrared.

Photolytic separation of isotopes in cryogenic solution

DOEpatents

Freund, Samuel M.; Maier, II, William B.; Holland, Redus F.; Beattie, Willard H.

1985-01-01

Separation of carbon isotopes by photolysis of CS.sub.2 in cryogenic solutions of nitrogen, krypton and argon with 206 nm light from an iodine resonance lamp is reported. The spectral distribution of the ultraviolet absorption depends on solvent. Thus, in liquid nitrogen the photolytic decomposition rate of .sup.13 CS.sub.2 is greater than that of .sup.12 CS.sub.2 (because the absorption of 206 nm radiation is greater for .sup.13 CS.sub.2), whereas in liquid krypton and liquid argon the reverse is true. The shift in ultraviolet spectrum is a general phenomenon readily characterized as a function of solvent polarizability, and exhibits behavior similar to that for vibrational transitions occurring in the infrared.

The application of UV LEDs for differential optical absorption spectroscopy

NASA Astrophysics Data System (ADS)

Geiko, Pavel P.; Smirnov, Sergey S.; Samokhvalov, Ignatii V.

2018-04-01

Modern UV LEDs represent a potentially very advantageous alternative to thermal light sources, in particular xenon arc lamps, which are the most common light sources in trace gas-analyzers. So, the light-emitting diodes are very attractive for use of as light sources for Long Path Differential Optical Absorption Spectroscopy (DOAS) measurements of trace gases in the open atmosphere. Recent developments in fibre-coupling telescope technology and the availability of ultraviolet light emitting diodes have now allowed us to construct a portable, long path DOAS instrument for use at remote locations and specifically for measuring degassing from active volcanic systems. First of all, we are talking about the measurement of sulphur dioxide, carbon disulphide and, oxides of chlorine and bromine. The parallel measurements of sulfur dioxide using a certified gas analyzer, were conducted and showed good correlation.

Vacuum and ultraviolet radiation effects on binders and pigments for spacecraft thermal control coatings

NASA Technical Reports Server (NTRS)

Progar, D. J.; Wade, W. R.

1971-01-01

An evaluation of several silicone resin binders and powdered inorganic pigments for potential use in spacecraft thermal-control paint formulations is presented. The pigments were selected on the basis of a hypothesis relating the heat of formation of a compound to the compound's resistance to ultra-radiation-induced degradation. Reflectance measurements were made in situ to determine degradation rates due to ultraviolet radiation. The tested polydimethylsiloxane resins were not significantly affected by long exposures to ultraviolet radiation. All the pigments, which were dispersed in a polydimethylsiloxane resin, were degraded by ultraviolet radiation as determined by an increase of solar absorptance. For the materials evaluated in this study, no evidence was found to indicate that pigments with high heats of formation were resistant to ultraviolet degradation.

Far Ultraviolet Spectroscopy of Saturn's Icy Moon Rhea

NASA Astrophysics Data System (ADS)

Elowitz, Mark; Hendrix, Amanda; Mason, Nigel J.; Sivaraman, Bhalamurugan

2018-01-01

We present an analysis of spatially resolved, far-UV reflectance spectra of Saturn’s icy satellite Rhea, collected by the Cassini Ultraviolet Imaging Spectrograph (UVIS). In recent years ultraviolet spectroscopy has become an important tool for analysing the icy satellites of the outer solar system (1Hendrix & Hansen, 2008). Far-UV spectroscopy provides unique information about the molecular structure and electronic transitions of chemical species. Many molecules that are suspected to be present in the icy surfaces of moons in the outer solar system have broad absorption features due to electronic transitions that occur in the far-UV portion of the spectrum. The studies show that Rhea, like the other icy satellites of the Saturnian system are dominated by water-ice as evident by the 165-nm absorption edge, with minor UV absorbing contaminants. Far-UV spectra of several Saturnian icy satellites, including Rhea and Dione, show an unexplained weak absorption feature centered near 184 nm. To carry out the geochemical survey of Rhea’s surface, the UVIS observations are compared with vacuum-UV spectra of thin-ice samples measured in laboratory experiments. Thin film laboratory spectra of water-ice and other molecular compounds in the solid phase were collected at near-vacuum conditions and temperatures identical to those at the surface of Rhea. Comparison between the observed far-UV spectra of Rhea’s surface ice and modelled spectra based on laboratory absorption measurements of different non-water-ice compounds show that two possible chemical compounds could explain the 184-nm absorption feature. The two molecular compounds include simple chlorine molecules and hydrazine monohydrate. Attempts to explain the source(s) of these compounds on Rhea and the scientific implications of their possible discovery will be summarized.[1] Hendrix, A. R. & Hansen, C. J. (2008). Icarus, 193, pp. 323-333.

Measurements of the intrinsic quantum efficiency and absorption length of tetraphenyl butadiene thin films in the vacuum ultraviolet regime

NASA Astrophysics Data System (ADS)

Benson, Christopher; Gann, Gabriel Orebi; Gehman, Victor

2018-04-01

A key enabling technology for many liquid noble gas (LNG) detectors is the use of the common wavelength shifting medium tetraphenyl butadiene (TPB). TPB thin films are used to shift ultraviolet scintillation light into the visible spectrum for detection and event reconstruction. Understanding the wavelength shifting efficiency and optical properties of these films are critical aspects in detector performance and modeling and hence in the ultimate physics sensitivity of such experiments. This article presents the first measurements of the room-temperature microphysical quantum efficiency for vacuum-deposited TPB thin films - a result that is independent of the optics of the TPB or substrate. Also presented are measurements of the absorption length in the vacuum ultraviolet regime, the secondary re-emission efficiency, and more precise results for the "black-box" efficiency across a broader spectrum of wavelengths than previous results. The low-wavelength sensitivity, in particular, would allow construction of LNG scintillator detectors with lighter elements (Ne, He) to target light mass WIMPs.

Spectrally-resolved measurements of aerosol extinction at ultraviolet and visible wavelengths

NASA Astrophysics Data System (ADS)

Flores, M.; Washenfelder, R. A.; Brock, C. A.; Brown, S. S.; Rudich, Y.

2012-12-01

Aerosols play an important role in the Earth's radiative budget. Aerosol extinction includes both the scattering and absorption of light, and these vary with wavelength, aerosol diameter, and aerosol composition. Historically, aerosol absorption has been measured using filter-based or extraction methods that are prone to artifacts. There have been few investigations of ambient aerosol optical properties at the blue end of the visible spectrum and into the ultraviolet. Brown carbon is particularly important in this spectral region, because it both absorbs and scatters light, and encompasses a large and variable group of organic compounds from biomass burning and secondary organic aerosol. We have developed a laboratory instrument that combines new, high-power LED light sources with high-finesse optical cavities to achieve sensitive measurements of aerosol optical extinction. This instrument contains two broadband channels, with spectral coverage from 360 - 390 nm and 385 - 420 nm. Using this instrument, we report aerosol extinction in the ultraviolet and near-visible spectral region as a function of chemical composition and structure. We have measured the extinction cross-sections between 360 - 420 nm with 0.5 nm resolution using different sizes and concentrations of polystyrene latex spheres, ammonium sulfate, and Suwannee River fulvic acid. Fitting the real and imaginary part of the refractive index allows the absorption and scattering to be determined.

High-resolution, vacuum-ultraviolet absorption spectrum of boron trifluoride

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hughes, Patrick P.; Thompson, Alan K.; Vest, Robert E.

2014-11-21

In the course of investigations of thermal neutron detection based on mixtures of {sup 10}BF{sub 3} with other gases, knowledge was required of the photoabsorption cross sections of {sup 10}BF{sub 3} for wavelengths between 135 and 205 nm. Large discrepancies in the values reported in existing literature led to the absolute measurements reported in this communication. The measurements were made at the SURF III Synchrotron Ultraviolet Radiation Facility at the National Institute of Standards and Technology. The measured absorption cross sections vary from 10{sup −20} cm{sup 2} at 135 nm to less than 10{sup −21} cm{sup 2} in the regionmore » from 165 to 205 nm. Three previously unreported absorption features with resolvable structure were found in the regions 135–145 nm, 150–165 nm, and 190–205 nm. Quantum mechanical calculations, using the TD-B3LYP/aug-cc-pVDZ variant of time-dependent density functional theory implemented in Gaussian 09, suggest that the observed absorption features arise from symmetry-changing adiabatic transitions.« less

The Copernicus ultraviolet spectral atlas of Vega

NASA Technical Reports Server (NTRS)

Rogerson, John B., Jr.

1989-01-01

A near-ultraviolet spectral atlas for the A0 V star Alpha Lyr (Vega) has been prepared from data taken by the Princeton spectrometer aboard the Copernicus satellite. The spectral region from 2000 to 3187 A has been scanned with a resolution of 0.1 A. The atlas is presented in graphs with a normalized continuum, and an identification table for the absorption features has been prepared.

Ultraviolet Broad Absorption Features and the Spectral Energy Distribution of the QSO PG 1351+64. 3.1

NASA Technical Reports Server (NTRS)

Zheng, W.; Kriss, G. A.; Wang, J. X.; Brotherton, M.; Oegerle, W. R.; Blair, W. P.; Davidsen, A. F.; Green, R. F.; Hutchings, J. B.; Kaiser, M. E.;

Ultraviolet Broad Absorption Features and the Spectral Energy Distribution of the QSO PG 1351+641. 2.5

NASA Technical Reports Server (NTRS)

Zheng, W.; Kriss, G. A.; Wang, J. X.; Brotherton, M.; Oegerle, W. R.; Blair, W. P.; Davidsen, A. F.; Green, R. F.; Hutchings, J. B.; Kaiser, M. E.;

Resistance of a lizard (the green anole, Anolis carolinensis; Polychridae) to ultraviolet radiation-induced immunosuppression

USGS Publications Warehouse

Cope, R.B.; Fabacher, D.L.; Lieske, C.; Miller, C.A.

2001-01-01

The green anole (Anolis carolinensis) is the most northerly distributed of its Neotropical genus. This lizard avoids a winter hibernation phase by the use of sun basking behaviors. Inevitably, this species is exposed to high doses of ambient solar ultraviolet radiation (UVR). Increases in terrestrial ultraviolet-B (UV-B) radiation secondary to stratospheric ozone depletion and habitat perturbation potentially place this species at risk of UVR-induced immunosuppression. Daily exposure to subinflammatory UVR (8 kJ/m2/day UV-B, 85 kJ/m2/day ultraviolet A [UV-A]), 6 days per week for 4 weeks (total cumulative doses of 192 kJ/m2 UV-B, 2.04 × 103 kJ/m2 UV-A) did not suppress the anole's acute or delayed type hypersensitivity (DTH) response to horseshoe crab hemocyanin. In comparison with the available literature UV-B doses as low as 0.1 and 15.9 kJ/m2 induced suppression of DTH responses in mice and humans, respectively. Exposure of anoles to UVR did not result in the inhibition of ex vivo splenocyte phagocytosis of fluorescein labeled Escherichia coli or ex vivo splenocyte nitric oxide production. Doses of UV-B ranging from 0.35 to 45 kJ/m2 have been reported to suppress murine splenic/peritoneal macrophage phagocytosis and nitric oxide production. These preliminary studies demonstrate the resistance of green anoles to UVR-induced immunosuppression. Methanol extracts of anole skin contained two peaks in the ultraviolet wavelength range that could be indicative of photoprotective substances. However, the resistance of green anoles to UVR is probably not completely attributable to absorption by UVR photoprotective substances in the skin but more likely results from a combination of other factors including absorption by the cutis and absorption and reflectance by various components of the dermis.

Chemical characterization of some aerobic liquids in CELSS

NASA Technical Reports Server (NTRS)

Madsen, Brooks C.

1993-01-01

Untreated aqueous soybean and wheat leachate and aerobically treated wheat leachate prepared from crop residues that are produced as a component of the Controlled Ecological Life Support System program designed to support long duration space missions were compared, and a general chemical characterization was accomplished. Solid phase extraction and high performance liquid chromatography were used to accomplish comparisons based on chromatographic and ultraviolet absorption properties of the components that are present. Specific compounds were not identified; however, general composition related to the initial presence of phenol-like compounds and their disappearance during aerobic treatment was explored.

High Harmonic Generation XUV Spectroscopy for Studying Ultrafast Photophysics of Coordination Complexes

NASA Astrophysics Data System (ADS)

Ryland, Elizabeth S.; Lin, Ming-Fu; Benke, Kristin; Verkamp, Max A.; Zhang, Kaili; Vura-Weis, Josh

2017-06-01

Extreme ultraviolet (XUV) spectroscopy is an inner shell technique that probes the M_{2,3}-edge excitation of atoms. Absorption of the XUV photon causes a 3p→3d transition, the energy and shape of which is directly related to the element and ligand environment. This technique is thus element-, oxidation state-, spin state-, and ligand field specific. A process called high-harmonic generation (HHG) enables the production of ultrashort (˜20fs) pulses of collimated XUV photons in a tabletop instrument. This allows transient XUV spectroscopy to be conducted as an in-lab experiment, where it was previously only possible at accelerator-based light sources. Additionally, ultrashort pulses provide the capability for unprecedented time resolution (˜50fs IRF). This technique has the capacity to serve a pivotal role in the study of electron and energy transfer processes in materials and chemical biology. I will present the XUV transient absorption instrument we have built, along with ultrafast transient M_{2,3}-edge absorption data of a series of small inorganic molecules in order to demonstrate the high specificity and time resolution of this tabletop technique as well as how our group is applying it to the study of ultrafast electronic dynamics of coordination complexes.

Far-infrared-light shadowgraphy for high extraction efficiency of extreme ultraviolet light from a CO2-laser-generated tin plasma

NASA Astrophysics Data System (ADS)

Matsukuma, Hiraku; Hosoda, Tatsuya; Suzuki, Yosuke; Yogo, Akifumi; Yanagida, Tatsuya; Kodama, Takeshi; Nishimura, Hiroaki

2016-08-01

The two-color, double-pulse method is an efficient scheme to generate extreme ultraviolet light for fabricating the next generation semiconductor microchips. In this method, a Nd:YAG laser pulse is used to expand a several-tens-of-micrometers-scale tin droplet, and a CO2 laser pulse is subsequently directed at the expanded tin vapor after an appropriate delay time. We propose the use of shadowgraphy with a CO2 laser probe-pulse scheme to optimize the CO2 main-drive laser. The distribution of absorption coefficients is derived from the experiment, and the results are converted to a practical absorption rate for the CO2 main-drive laser.

Enhanced Photocatalytic Activity of La3+-Doped TiO2 Nanotubes with Full Wave-Band Absorption

NASA Astrophysics Data System (ADS)

Xia, Minghao; Huang, Lingling; Zhang, Yubo; Wang, Yongqian

2018-06-01

TiO2 nanotubes doped with La3+ were synthesized by anodic oxidation method and the photocatalytic activity was detected by photodegrading methylene blue. As-prepared samples improved the absorption of both ultraviolet light and visible light and have a great enhancement on the photocatalytic activity while contrasting with the pristine TiO2 nanotubes. A tentative mechanism for the enhancement of photocatalytic activity with full wave-band absorption is proposed.

Rapid and on-site analysis of illegal drugs on the nano-microscale using a deep ultraviolet-visible reflected optical fiber sensor.

PubMed

Li, Qiang; Qiu, Tian; Hao, Hongxia; Zhou, Hong; Wang, Tongzhou; Zhang, Ye; Li, Xin; Huang, Guoliang; Cheng, Jing

2012-04-07

A deep ultraviolet-visible (DUV-Vis) reflected optical fiber sensor was developed for use in a simple spectrophotometric detection system to detect the absorption of various illegal drugs at wavelengths between 180 and 800 nm. Quantitative analyses performed using the sensor revealed a high specificity and sensitivity for drug detection at a wavelength of approximately 200 nm. Using a double-absorption optical path length, extremely small sample volumes were used (32 to 160 nL), which allowed the use of minimal amounts of samples. A portable spectrophotometric system was established based on our optical fiber sensor for the on-site determination and quantitative analysis of common illegal drugs, such as 3,4-methylenedioxymethamphetamine (MDMA), ketamine hydrochloride, cocaine hydrochloride, diazepam, phenobarbital, and barbital. By analyzing the absorbance spectra, six different drugs were quantified at concentrations that ranged from 0.1 to 1000 μg mL(-1) (16 pg-0.16 μg). A novel Matching Algorithm of Spectra Space (MASS) was used to accurately distinguish between each drug in a mixture. As an important supplement to traditional methods, such as mass spectrometry or chromatography, our optical fiber sensor offers rapid and low-cost on-site detection using trace amounts of sample. This rapid and accurate analytical method has wide-ranging applications in forensic science, law enforcement, and medicine.

Laboratory measurement of the absorption coefficient of riboflavin for ultraviolet light (365 nm).

PubMed

Iseli, Hans Peter; Popp, Max; Seiler, Theo; Spoerl, Eberhard; Mrochen, Michael

2011-03-01

Corneal cross-linking (CXL) is an increasingly used treatment technique for stabilizing the cornea in keratoconus. Cross-linking (polymerization) between collagen fibrils is induced by riboflavin (vitamin B2) and ultraviolet light (365 nm). Although reported to reach a constant value at higher riboflavin concentrations, the Lambert-Beer law predicts a linear increase in the absorption coefficient. This work was carried out to determine absorption behavior at different riboflavin concentrations and to further investigate the purported plateau absorption coefficient value of riboflavin and to identify possible bleaching effects. The Lambert-Beer law was used to calculate the absorption coefficient at various riboflavin concentrations. The following investigated concentrations of riboflavin solutions were prepared using a mixture of 0.5% riboflavin and 20% Dextran T500 dissolved in 0.9% sodium chloride solution: 0%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.08%, 0.1%, 0.2%, 0.3%, 0.4%, and 0.5%, and were investigated with and without aperture plate implementation. An additional test series measured the transmitted power at selected riboflavin concentrations over time. In diluted solutions, a linear correlation exists between the absorption coefficient and riboflavin concentration. The absorption coefficient reaches a plateau, but this occurs at a higher riboflavin concentration (0.1%) than previously reported (just above 0.04%). Transmitted light power increases over time, indicating a bleaching effect of riboflavin. The riboflavin concentration can be effectively varied as a treatment parameter in a considerably broader range than previously thought. Copyright 2011, SLACK Incorporated.

Spectrophotometric Attachment for the Vacuum Ultraviolet

NASA Technical Reports Server (NTRS)

Axelrod, Norman N.

1961-01-01

An absorption spectrophotometric attachment to a vacuum ultraviolet monochromator has been built and tested. With an empty sample chamber, the ratio of the radiant flux through the sample chamber to the radiant flux through the reference chamber was measured. By optimizing conditions at the entrance slit, the ratio was constant within experimental error over the region 1000-1600 A. The transmittance of thin celluloid films was measured with the attachment.

Photodetection and Photoswitch Based On Polarized Optical Response of Macroscopically Aligned Carbon Nanotubes.

PubMed

Zhang, Ling; Wu, Yang; Deng, Lei; Zhou, Yi; Liu, Changhong; Fan, Shoushan

2016-10-12

Light polarization is extensively applied in optical detection, industry processing and telecommunication. Although aligned carbon nanotube naturally suppresses the transmittance of light polarized parallel to its axial direction, there is little application regarding the photodetection of carbon nanotube based on this anisotropic interaction with linearly polarized light. Here, we report a photodetection device realized by aligned carbon nanotube. Because of the different absorption behavior of polarized light with respect to polarization angles, such device delivers an explicit response to specific light wavelength regardless of its intensity. Furthermore, combining both experimental and mathematical analysis, we found that the light absorption of different wavelength causes characteristic thermoelectric voltage generation, which makes aligned carbon nanotube promising in optical detection. This work can also be utilized directly in developing new types of photoswitch that features a broad spectrum application from near-ultraviolet to intermediate infrared with easy integration into practical electric devices, for instance, a "wavelength lock".

Phage-directed synthesis of copper sulfide: structural and optical characterization

NASA Astrophysics Data System (ADS)

Shahriar Zaman, Mohammed; Moon, Chung Hee; Bozhilov, Krassimir N.; Haberer, Elaine D.

2013-08-01

The growth of crystalline copper sulfide using a viral template was investigated using sequential incubation in CuCl2 and Na2S precursors. Non-specific electrostatic attraction between a genetically-modified M13 bacteriophage and copper cations in the CuCl2 precursor caused phage agglomeration and bundle formation. Following the addition of Na2S, polydisperse nanocrystals 2-7 nm in size were found along the length of the viral scaffold. The structure of the copper sulfide material was identified as cubic anti-fluorite type Cu1.8S, space group F m\\bar {3}m. Strong interband absorption was observed within the ultraviolet to visible range with an onset near 800 nm. Furthermore, free carrier absorption, associated with the localized surface plasmon resonance of the copper sulfide nanocrystals, was seen in the near infrared with absorbance maxima at 1060 nm and 3000 nm, respectively.

0.5-keV Soft X-ray attosecond continua

PubMed Central

Teichmann, S. M.; Silva, F.; Cousin, S. L.; Hemmer, M.; Biegert, J.

2016-01-01

Attosecond light pulses in the extreme ultraviolet have drawn a great deal of attention due to their ability to interrogate electronic dynamics in real time. Nevertheless, to follow charge dynamics and excitations in materials, element selectivity is a prerequisite, which demands such pulses in the soft X-ray region, above 200 eV, to simultaneously cover several fundamental absorption edges of the constituents of the materials. Here, we experimentally demonstrate the exploitation of a transient phase matching regime to generate carrier envelope controlled soft X-ray supercontinua with pulse energies up to 2.9±0.1 pJ and a flux of (7.3±0.1) × 107 photons per second across the entire water window and attosecond pulses with 13 as transform limit. Our results herald attosecond science at the fundamental absorption edges of matter by bridging the gap between ultrafast temporal resolution and element specific probing. PMID:27167525

Complete erasing of ghost images caused by deeply trapped electrons on computed radiography plates

NASA Astrophysics Data System (ADS)

Ohuchi, H.; Kondo, Y.

2011-03-01

The ghost images, i.e., latent image that is unerasable with visible light (LIunVL) and reappearing image appeared on computed radiography (CR) plates were completely erased by simultaneous exposing them to filtered ultraviolet light and visible light. Three different types of CR plates (Agfa, Kodak, and Fuji) were irradiated with 50 kV X-ray beams in the dose range 8.1 mGy to 8.0 Gy, and then conventionally erased for 2 h with visible light. The remaining LIunVL could be erased by repeating 6 h simultaneous exposures to filtered ultraviolet light and visible light. After the sixth round of exposure, all the LIunVL in the three types of CR plates were erased to the same level as in an unirradiated plate and no latent images reappeared after storage at 0°C for 14 days. The absorption spectra of deep centers were specified using polychromatic ultraviolet light from a deep-ultraviolet lamp. It was found that deep centers showed a dominant peak in the absorption spectra at around 324 nm for the Agfa and Kodak plates, and at around 320 nm for the Fuji plate, in each case followed by a few small peaks. After completely erasing CR plates, these peaks were no longer observed.

Elucidating ultrafast electron dynamics at surfaces using extreme ultraviolet (XUV) reflection-absorption spectroscopy.

PubMed

Biswas, Somnath; Husek, Jakub; Baker, L Robert

2018-04-24

Here we review the recent development of extreme ultraviolet reflection-absorption (XUV-RA) spectroscopy. This method combines the benefits of X-ray absorption spectroscopy, such as element, oxidation, and spin state specificity, with surface sensitivity and ultrafast time resolution, having a probe depth of only a few nm and an instrument response less than 100 fs. Using this technique we investigated the ultrafast electron dynamics at a hematite (α-Fe2O3) surface. Surface electron trapping and small polaron formation both occur in 660 fs following photoexcitation. These kinetics are independent of surface morphology indicating that electron trapping is not mediated by defects. Instead, small polaron formation is proposed as the likely driving force for surface electron trapping. We also show that in Fe2O3, Co3O4, and NiO, band gap excitation promotes electron transfer from O 2p valence band states to metal 3d conduction band states. In addition to detecting the photoexcited electron at the metal M2,3-edge, the valence band hole is directly observed as transient signal at the O L1-edge. The size of the resulting charge transfer exciton is on the order of a single metal-oxygen bond length. Spectral shifts at the O L1-edge correlate with metal-oxygen bond covalency, confirming the relationship between valence band hybridization and the overpotential for water oxidation. These examples demonstrate the unique ability to measure ultrafast electron dynamics with element and chemical state resolution using XUV-RA spectroscopy. Accordingly, this method is poised to play an important role to reveal chemical details of previously unseen surface electron dynamics.

Exciplex formation and electroluminescent absorption in ultraviolet organic light-emitting diodes

NASA Astrophysics Data System (ADS)

Zhang, Qi; Zhang, Hao; Zhang, Xiao-Wen; Xu, Tao; Wei, Bin

2015-02-01

We investigated the formation of exciplex and electroluminescent absorption in ultraviolet organic light-emitting diodes (UV OLEDs) using different heterojunction structures. It is found that an energy barrier of over 0.3 eV between the emissive layer (EML) and adjacent transport layer facilitates exciplex formation. The electron blocking layer effectively confines electrons in the EML, which contributes to pure UV emission and enhances efficiency. The change in EML thickness generates tunable UV emission from 376 nm to 406 nm. In addition, the UV emission excites low-energy organic function layers and produces photoluminescent emission. In UV OLED, avoiding the exciplex formation and averting light absorption can effectively improve the purity and efficiency. A maximum external quantum efficiency of 1.2% with a UV emission peak of 376 nm is realized. Project supported by the National Natural Science Foundation of China (Grant Nos. 61136003 and 61275041) and the Guangxi Provincial Natural Science Foundation, China (Grant No. 2012GXNSFBA053168).

Ultra-violet absorption induced modifications in bulk and nanoscale electrical transport properties of Al-doped ZnO thin films

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kumar, Mohit; Basu, Tanmoy; Som, Tapobrata, E-mail: tsom@iopb.res.in

Using conductive atomic force microscopy and Kelvin probe force microscopy, we study local electrical transport properties in aluminum-doped zinc oxide (ZnO:Al or AZO) thin films. Current mapping shows a spatial variation in conductivity which corroborates well with the local mapping of donor concentration (∼10{sup 20 }cm{sup −3}). In addition, a strong enhancement in the local current at grains is observed after exposing the film to ultra-violet (UV) light which is attributed to persistent photocurrent. Further, it is shown that UV absorption gives a smooth conduction in AZO film which in turn gives rise to an improvement in the bulk photoresponsivity ofmore » an n-AZO/p-Si heterojunction diode. This finding is in contrast to the belief that UV absorption in an AZO layer leads to an optical loss for the underneath absorbing layer of a heterojunction solar cell.« less

The measurement of acetanilide in plasma by spectrophotometric and selected ion monitoring methods.

PubMed

Baty, J D; Playfer, J; Evans, D A; Lamb, J

1977-08-01

Plasma samples from volunteers who had received an oral dose of acetanilide have been analysed by gas chromatography mass spectrometry and ultraviolet absorption techniques. The gas chromatography mass spectrometry method involved extraction of the plasma and analysis of the acetanilide using selected ion monitoring with a deuterated internal standard. In the ultraviolet method the plasma was hydrolysed with acid to convert the acetanilide to aniline, and this compound was diazotized and coupled with N-1-naphthylethylene-diamine. The absorbance of the resulting complex was read at 550 nm. Acetanilide levels in plasma determined by the selected ion monitoring method were significantly lower than those measured by spectrophotometry. Pharmacokinetic data calculated from the results obtained using these two assays are very different and illustrate the need for an accurate and specific method of analysis. The major metabolites of acetanilide are shown not to interfere with these assays and the results suggest the possible presence of a new metabolite of acetanilide.

[Experimental research of turbidity influence on water quality monitoring of COD in UV-visible spectroscopy].

PubMed

Tang, Bin; Wei, Biao; Wu, De-Cao; Mi, De-Ling; Zhao, Jing-Xiao; Feng, Peng; Jiang, Shang-Hai; Mao, Ben-Jiang

2014-11-01

Eliminating turbidity is a direct effect spectroscopy detection of COD key technical problems. This stems from the UV-visible spectroscopy detected key quality parameters depend on an accurate and effective analysis of water quality parameters analytical model, and turbidity is an important parameter that affects the modeling. In this paper, we selected formazine turbidity solution and standard solution of potassium hydrogen phthalate to study the turbidity affect of UV--visible absorption spectroscopy detection of COD, at the characteristics wavelength of 245, 300, 360 and 560 nm wavelength point several characteristics with the turbidity change in absorbance method of least squares curve fitting, thus analyzes the variation of absorbance with turbidity. The results show, In the ultraviolet range of 240 to 380 nm, as the turbidity caused by particle produces compounds to the organics, it is relatively complicated to test the turbidity affections on the water Ultraviolet spectra; in the visible region of 380 to 780 nm, the turbidity of the spectrum weakens with wavelength increases. Based on this, this paper we study the multiplicative scatter correction method affected by the turbidity of the water sample spectra calibration test, this method can correct water samples spectral affected by turbidity. After treatment, by comparing the spectra before, the results showed that the turbidity caused by wavelength baseline shift points have been effectively corrected, and features in the ultraviolet region has not diminished. Then we make multiplicative scatter correction for the three selected UV liquid-visible absorption spectroscopy, experimental results shows that on the premise of saving the characteristic of the Ultraviolet-Visible absorption spectrum of water samples, which not only improve the quality of COD spectroscopy detection SNR, but also for providing an efficient data conditioning regimen for establishing an accurate of the chemical measurement methods.

Spectroscopic, orbital, and physical properties of the binary Feige 24 and detection of transient He II absorption in the system

NASA Technical Reports Server (NTRS)

Vennes, Stephane; Thorstensen, John R.

1994-01-01

We have obtained new high-dispersion optical spectroscopy at Kitt Peak National Observatory (KPNO) and new International Ultraviolet Explorer (IUE) spectroscopy of the white dwarf+red dwarf binary system Feige 24. The optical range shows a composite DA+dM spectrum, together with H I Balmer and He I emission. The orbital phase dependence of the emission shows that it results from extreme ultraviolet (EUV) light reprocessing in the red dwarf upper atmosphere. The systems close enough and hot enough to show this reprocessing signature only recently emerged from common-envelope evolution. The ultraviolet spectrum exclusively emanates from the white dwarf and shows numerous heavy element absorption lines. We measured accurate radial velocities of the red dwarf component motion, traced by both optical absorption and emission lines, and new radial velocities of the white dwarf, traced by ultraviolet Fe V lines. Combining these measurements, we refined the orbital parameters presented by Vennes et al. (1991), and we confirmed that the white dwarf gravitational redshift is exceptionally small with 9 +/- 2 km/s. From this we deduced that the interior is either pure helium or carbon with a thick hydrogen layer, and we derived, for the combined interior compositions, a white dwarf mass and radius of M(sub WD) = 0.44-050 solar mass and R(sub WD) = 0.028-0.036 solar radius. We suggest that Feige 24 could be a typical case of close binary evolution leading to the formation of a low-mass helium white dwarf. The mass of the red dwarf and the inclination of the system naturally follow: M(sub dM) = 0.26-0.33 solar mass, i greater than or equal to 75 deg. High-dispersion H-alpha line profiles are asymmetrical, strongly enhanced toward the blue, suggesting a moving atmosphere possibly linked to a mass loss rate of 10(exp -10) solar mass/yr. The IUE spectra taken when the system is near inferior conjunction show strong He II 1640 A absorption. The profile is highly variable in width and intensity. Because it is correlated with the passage of the white dwarf at inferior conjunction, the absorption may occur in some foreground plasma emanated by the red dwarf and accumulating near a Lagrangian point or, alternatively, it may originate in an accretion spot on the white dwarf surface coaligned with the major orbital axis. Either way, the He II detection may imply substantial mass loss from the red dwarf with a corollary reclassification of Feige 24 as a mixed He/H DAO white dwarf resulting from accretion of secondary mass-loss material. Feige 24 is the prototype of a class of young, EUV-emitting, binary systems comprising a late main sequence secondary and a hot H-rich white dwarf; the class is characterized by optical and ultraviolet photospheric He II absorption, circumstellar C IV lambda (1550) absorption, and by the presence of EUV-induced, phase-dependent Balmer fluorescence. These young systems present the best opportunity to constrain theory of common-envelope evolution.

Ultraviolet Imaging Telescope images of the reflection nebula NGC 7023 - Derivation of ultraviolet scattering properties of dust grains

NASA Technical Reports Server (NTRS)

Witt, Adolf N.; Petersohn, Jens K.; Bohlin, Ralph C.; O'Connell, Robert W.; Roberts, Morton S.; Smith, Andrew M.; Stecher, Theodore P.

1992-01-01

The Ultraviolet Imaging Telescope as part of the Astro-1 mission, was used to obtain high-resolution surface brightness distribution data in six ultraviolet wavelength bands for the bright reflection nebula NGC 7023. From the quantitative comparison of the measured surface brightness gradients ratios of nebular to stellar flux, and detail radial surface brightness profiles with corresponding data from the visible, two major conclusions results: (1) the scattering in the near- and far-ultraviolet in this nebula is more strongly forward-directed than in the visible; (2) the dust albedo in the ultraviolet for wavelengths not less than 140 nm is identical to that in the visible, with the exception of the 220 nm bump in the extinction curve. In the wavelengths region of the bump, the albedo is reduced by 25 to 30 percent in comparison with wavelengths regions both shorter and longer. This lower albedo is expected, if the bump is a pure absorption feature.

Ultraviolet Views of Enceladus, Tethys, and Dione

NASA Technical Reports Server (NTRS)

Hansen, C. J.; Hendrix, A. R.

2005-01-01

The Cassini Ultraviolet Imaging Spectrograph (UVIS) has collected ultraviolet observations of many of Saturn's icy moons since Cassini's insertion into orbit around Saturn. We will report on results from Enceladus, Tethys and Dione, orbiting in the Saturn system at distances of 3.95, 4.88 and 6.26 Saturn radii, respectively. Icy satellite science objectives of the UVIS include investigations of surface age and evolution, surface composition and chemistry, and tenuous exospheres. We address these objectives by producing albedo maps, and reflection and emission spectra, and observing stellar occultations. UVIS has four channels: EUV: Extreme Ultraviolet (55 nm to 110 nm), FUV: Far Ultraviolet (110 to 190 nm), HSP: High Speed Photometer, and HDAC: Hydrogen-Deuterium Absorption Cell. The EUV and FUV spectrographs image onto a 2-dimensional detector, with 64 spatial rows by 1024 spectral columns. To-date we have focused primarily on the far ultraviolet data acquired with the low resolution slit width (4.8 angstrom spectral resolution). Additional information is included in the original extended abstract.

Characterization of Lignin in Situ by Photoacoustic Spectroscopy

PubMed Central

Gould, J. Michael

1982-01-01

Photoacoustic spectroscopy is a recently developed nondestructive analytical technique that provides ultraviolet, visible, and infrared absorption spectra from intensely light scattering, solid, and/or optically opaque materials not suitable for conventional spectrophotometric analysis. In wood and other lignocellulosics, the principal ultraviolet absorption bands, in the absence of photosynthetic pigments, arise from the aromatic lignin component of the cell walls. Photoacoustic spectra of extracted lignin fragments (milled wood lignin) and synthetic lignin-like polymers contain a single major absorption band at 280 nanometers with an absorption tail extending beyond 400 nanometers. Photoacoustic spectra of pine, maple, and oak lignin in situ contain a broad primary absorption band at 300 nanometers and a longer wavelength shoulder around 370 nanometers. Wheat lignin in situ, on the other hand, exhibits two principle absorption peaks, at 280 nanometers and 320 nanometers. The presence of absorption bands at wavelengths greater than 300 nanometers in intact lignin could result from (a) interacting, nonconjugated chromophores, or (b) the presence of more highly conjugated structural components formed as the result of oxidation of the polymer. Evidence for the latter comes from the observation that, on the outer surface of senescent, field-dried wheat culms (stems), new absorption bands in the 350 to 400 nanometer region predominate. These new bands are less apparent on the outer surface of presenescent wheat culms and are virtually absent on the inner surface of either senescent or presenescent culms, suggesting that the appearance of longer wavelength absorption bands in senescent wheat is the result of accumulated photochemical modifications of the ligin polymer. These studies also demonstrate photoacoustic spectroscopy to be an important new tool for the investigation of insoluble plant components. PMID:16662709

Ultraviolet absorption by highly ionized atoms in the Orion Nebula

NASA Technical Reports Server (NTRS)

Franco, J.; Savage, B. D.

1982-01-01

The International Ultraviolet Explorer was used to obtain high-resolution, far-UV spectra of theta 1 A, theta 1 C, theta 1 D, and theta 2 A Orionis. The interstellar absorption lines in these spectra are discussed with an emphasis on the high-ionization lines of C IV and Si IV. Theta 2 A Ori has interstellar C IV and Si IV absorption of moderate strength at the velocity found for normal H II region ions. Theta 1 C Ori has very strong interstellar C IV and Si IV absorption at velocities blueshifted by about 25 km/s from that found for the normal H II region ions. The possible origin of the high-ionization lines by three processes is considered: X-ray ionization, collisional ionization, and UV photoionization. It is concluded that the C IV and Si IV ions toward theta 2 A and theta 1 C Ori are likely produced by UV photoionization of surrounding nebular gas. In the case of theta 1 C Ori, the velocity shift of the high-ionization lines may be produced through the acceleration of high-density globules in the core of the nebula by the stellar wind of theta 1 C Ori.

Uric acid detection using uv-vis spectrometer

NASA Astrophysics Data System (ADS)

Norazmi, N.; Rasad, Z. R. Abdul; Mohamad, M.; Manap, H.

2017-10-01

The aim of this research is to detect uric acid (UA) concentration using Ultraviolet-Visible (UV-Vis) spectrometer in the Ultraviolet (UV) region. Absorption technique was proposed to detect different uric acid concentrations and its UV absorption wavelength. Current practices commonly take a lot of times or require complicated structures for the detection process. By this proposed spectroscopic technique, every concentration can be detected and interpreted into an absorbance value at a constant wavelength peak in the UV region. This is due to the chemical characteristics belong to the uric acid since it has a particular absorption cross-section, σ which can be calculated using Beer’s Lambert law formula. The detection performance was displayed using Spectrasuite sofware. It showed fast time response about 3 seconds. The experiment proved that the concentrations of uric acid were successfully detected using UV-Vis spectrometer at a constant absorption UV wavelength, 294.46 nm in a low time response. Even by an artificial sample of uric acid, it successfully displayed a close value as the ones reported with the use of the medical sample. It is applicable in the medical field and can be implemented in the future for earlier detection of abnormal concentration of uric acid.

The Loopy Ultraviolet Line Profiles of RU Lupi: Accretion, Outflows, and Fluorescence

NASA Astrophysics Data System (ADS)

Herczeg, Gregory J.; Walter, Frederick M.; Linsky, Jeffrey L.; Gahm, Gösta F.; Ardila, David R.; Brown, Alexander; Johns-Krull, Christopher M.; Simon, Michal; Valenti, Jeff A.

2005-06-01

We present far-ultraviolet (FUV) spectra of the classical T Tauri star RU Lup covering the 912-1710 Å spectral range, as observed by the Hubble Space Telescope STIS and the Far Ultraviolet Spectroscopic Explorer satellite. We use these spectra, which are rich in emission and absorption lines, to probe both the accreting and outflowing gas. Absorption in the Lyα profile constrains the extinction to AV~0.07 mag, which we confirm with other diagnostics. We estimate a mass accretion rate of (5+/-2)×10-8 Msolar yr-1 using the optical-NUV accretion continuum. The accreting gas is also detected in bright, broad lines of C IV, Si IV, and N V, which all show complex structures across the line profile. Many other emission lines, including those of H2 and Fe II, are pumped by Lyα. RU Lup's spectrum varies significantly in the FUV; our STIS observations occurred when RU Lup was brighter than several other observations in the FUV, possibly because of a high mass accretion rate.

Comparison of ozone determinations by ultraviolet photometry and gas-phase titration

NASA Technical Reports Server (NTRS)

Demore, W. B.; Patapoff, M.

1976-01-01

A comparison of ozone determinations based on ultraviolet absorption photometry and gas-phase titration (GPT) shows good agreement between the two methods. Together with other results, these findings indicate that three candidate reference methods for ozone, UV photometry, IR photometry, and GPT are in substantial agreement. However, the GPT method is not recommended for routine use by air pollution agencies for calibration of ozone monitors because of susceptibility to experimental error.

Magnetic fluorescent lamp having reduced ultraviolet self-absorption

DOEpatents

Berman, Samuel M.; Richardson, Robert W.

1985-01-01

The radiant emission of a mercury-argon discharge in a fluorescent lamp assembly (10) is enhanced by providing means (30) for establishing a magnetic field with lines of force along the path of electron flow through the bulb (12) of the lamp assembly, to provide Zeeman splitting of the ultraviolet spectral line. Optimum results are obtained when the magnetic field strength causes a Zeeman splitting of approximately 1.7 times the thermal line width.

NARSTO EPA SS HOUSTON TEXAQS2000 DOE G-1 DATA

Atmospheric Science Data Center

2018-04-09

... Dioxide Formaldehyde Particulate Matter Ultraviolet Radiation Absorption Carbon Monoxide Hydrogen Peroxides Sulfate ... Earth Related Data:  Environmental Protection Agency Supersites Houston, Texas SCAR-B Block:  ...

Ultraviolet reflectance properties of asteroids

NASA Astrophysics Data System (ADS)

Butterworth, P. S.; Meadows, A. J.

1985-05-01

An analysis of the UV spectra of 28 asteroids obtained with the Internal Ultraviolet Explorer (IUE) satellite is presented. The spectra lie within the range 2100-3200 A. The results are examined in terms of both asteroid classification and of current ideas concerning the surface mineralogy of asteroids. For all the asteroids examined, UV reflectivity declines approximately linearly toward shorter wavelengths. In general, the same taxonomic groups are seen in the UV as in the visible and IR, although there is some evidence for asteroids with anomalous UV properties and for UV subclasses within the S class. No mineral absorption features are reported of strength similar to the strongest features in the visible and IR regions, but a number of shallow absorptions do occur and may provide valuable information on the surface composition of many asteroids.

Electronic absorption spectroscopy of matrix-isolated polycyclic aromatic hydrocarbon cations. II. The phenanthrene cation (C14H10+) and its 1-methyl derivative

NASA Technical Reports Server (NTRS)

Salama, F.; Joblin, C.; Allamandola, L. J.

1994-01-01

The ultraviolet, visible, and near infrared absorption spectra of phenanthrene (C14H10), 1-methylphenanthrene [(CH3)C14H9], and their radical ions [C14H10+; (CH3)C14H9+], formed by vacuum-ultraviolet irradiation, were measured in neon matrices at 4.2 K. The associated vibronic band systems and their spectroscopic assignments are discussed. The oscillator strengths were calculated for the phenanthrene ion and found lower than the theoretical predictions. This study presents the first spectroscopic data for phenanthrene and its methyl derivative trapped in a neon matrix where the perturbation of the isolated species by its environment is minimum; a condition crucial to astrophysical applications.

Results of the examination of LDEF polyurethane thermal control coatings

NASA Technical Reports Server (NTRS)

Golden, Johnny L.

1994-01-01

This report summarizes the condition of polyurethane thermal control coatings subjected to 69 months of low earth orbit (LEO) exposure on the Long Duration Exposure Facility (LDEF) mission. Specimens representing all environmental aspects obtainable by LDEF were analyzed. Widely varying changes in the thermo-optical and mechanical properties of these materials were observed, depending on atomic oxygen and ultraviolet radiation fluences. High atomic oxygen fluences, regardless of ultraviolet radiation exposure levels, resulted in near original optical properties for these coatings but with a degradation in their mechanical condition. A trend in solar absorptance increase with ultraviolet radiation fluence was observed. Contamination, though observed, exhibited minimal effects.

[Analysis of UV-visible absorption spectrum on the decolorization of industrial wastewater by disinfection].

PubMed

Huang, Xin; Wang, Long-Yong; Gao, Nai-Yun; Li, Wei-Guo

2012-10-01

The UV-Visible absorption spectrum of industrial wastewater was explored to introduce a substituting method determining the color of water, and to compare the decolorization efficacy of different disinfectants. The results show that the visible absorption spectrum(350-600 nm), instead of ultraviolet absorption spectrum, should be applied to characterize the color of wastewater. There is a good correlation between the features of visible absorption spectrum and the true color of wastewater. Both ozone and chlorine dioxide has a better decolorization performance than chlorine. However, the color of chlorine dioxide itself has a negative effect on decolorization. The changes in the features of visible absorption spectrum effectively reflect the variations in the color of wastewater after disinfection.

The polarization and ultraviolet spectrum of Markarian 231

NASA Technical Reports Server (NTRS)

Smith, Paul S.; Schmidt, Gary D.; Allen, Richard G.; Angel, J. R. P.

1995-01-01

Ultraviolet spectropolarimetry acquired with the Hubble Space Telescope (HST) of the peculiar Seyfert galaxy Mrk 231 is combined with new high-quality ground-based measurements to provide the first, nearly complete, record of its linear polarization from 1575 to 7900 A. The accompanying ultraviolet spectrum portrays the heavily extinguished emission-line spectrum of the active nucleus plus the emergence of a blue continuum shortward of approximately 2400 A. In addition, absorption features due to He I lambda 3188, Mg I lambda 2853, Mg II lambda 2798, and especially several resonance multiplets of Fe II are identified with a well-known optical absorption system blueshifted approximately 4600 km/s with respect to emission lines. The continuum is attributed to approximately 10(exp 5) hot, young stars surrounding the nucleus. This component dilutes the polarized nuclear light, implying that the intrinsic polarization of the active galactic nucleus (AGN) spectrum approaches 20% at 2800 A. The rapid decline in degree of polarization toward longer wavelengths is best explained by the strongly frequency-dependent scattering cross section of dust grains coupled with modest starlight dilution. Peculiar S-shaped inflections in both the degree and position angle of polarization through H alpha and other major emission lines are interpreted as effects of scattering from two regions offset in velocity by several hundred km/s. A third source of (weakly) polarized flux is required to explain a nearly 40 deg rotation in position angle between 3200 and 1800 A. The displaced absorption features, polarimetry, and optical/infrared properties of Mrk 231 all point to its classification as a low-ionization, or Mg II broad absorption line quasar, in which most, if not all, lines of sight to the active nucleus are heavily obscured by dust and low-ionization gas clouds.

The absorption characteristics of the human cornea in ultraviolet-a crosslinking.

PubMed

Koppen, Carina; Gobin, Laure; Tassignon, Marie-José

2010-03-01

With respect to the safety of ultraviolet-A (UVA) crosslinking for the corneal endothelium, an absorption coefficient is used that has been calculated in riboflavin soaked porcine corneas. We aim to validate this value for clinical use by measuring the absorption coefficient for UVA 365 nm in postmortem human corneas after instilling riboflavin on the corneal surface. Corneal thickness was measured in nine pairs of human donor eyes of which one eye was subjected to manual removal of the epithelium, whereas the epithelium of the fellow eye was left intact. Both eyes were instilled with riboflavin 0.1% in dextran 20% on the intact globe. After 20 min, the corneas were rinsed, and a corneoscleral button was trephined. The transmission of the cornea for UVA 365 nm was measured by transillumination, which allows calculation of the absorption coefficient. Measurement of average corneal thickness was 658.5 +/- 51.5 microm when the epithelium was removed, and 758.3 +/- 98.8 microm without epithelial removal. The average transmittance for UVA 365 nm was 12.89 +/- 4.10% with epithelial debridement and 28.52 +/- 4.39% without (P<0.05). The resultant average absorption coefficient is 32 +/- 5 cm when the epithelium is removed and 17 +/- 2 cm when it is left intact (P<0.05). Our results show an absorption coefficient for human corneas that is much lower than the values reported in the literature. This finding may be relevant when considering endothelial safety of the clinical crosslinking treatment.

Far Ultraviolet Spectroscopic Explorer Observations of the Seyfert 1.5 Galaxy NGC 5548 in a Low State

NASA Technical Reports Server (NTRS)

Brotherton, M. S.; Green, R. F.; Kriss, G. A.; Oegerle, W.; Kaiser, M. E.; Zheng, W.; Hutchings, J. B.; Fisher, Richard R. (Technical Monitor)

2001-01-01

We present far-ultraviolet spectra of the Seyfert 1.5 galaxy NGC 5548 obtained in 2000 June with the Far Ultraviolet Spectroscopic Explorer (FUSE). Our data span the observed wavelength range 915-1185 A at a resolution of approximately 20 km s(exp -1). The spectrum shows a weak continuum and emission from O VI (lambda)(lambda)1032, 1038, C III (lambda)977, and He II (lambda)1085. The FUSE data were obtained when the AGN (Active Galactic Nuclei) was in a low state, which has revealed strong, narrow O VI emission lines. We also resolve intrinsic, associated absorption lines of O VI and the Lyman series. Several distinct kinematic components are present, spanning a velocity range of approximately 0 to -1300 km s(exp -1) relative to systemic, with kinematic structure similar to that seen in previous observations of longer wavelength ultraviolet (UV) lines. We explore the relationships between the far-UV (ultraviolet) absorbers and those seen previously in the UV and X-rays. We find that the high-velocity UV absorption component is consistent with being low-ionization, contrary to some previous claims, and is consistent with its non-detection in high-resolution X-ray spectra. The intermediate velocity absorbers, at -300 to -400 km s(exp -1), show H I and O VI column densities consistent with having contributions from both a high-ionization X-ray absorber and a low-ionization UV absorber. No single far-UV absorbing component can be solely identified with the X-ray absorber.

Theoretical Prediction of Si 2–Si 33 Absorption Spectra

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhao, Li -Zhen; Lu, Wen -Cai; Qin, Wei

Here, the optical absorption spectra of Si 2–Si 33 clusters were systematically studied by a time-dependent density functional theory approach. The calculations revealed that the absorption spectrum becomes significantly broad with increasing cluster size, stretching from ultraviolet to the infrared region. The absorption spectra are closely related to the structural motifs. With increasing cluster size, the absorption intensity of cage structures gradually increases, but the absorption curves of the prolate and the Y-shaped structures are very sensitive to cluster size. If the transition energy reaches ~12 eV, it is noted that all the clusters have remarkable absorption in deep ultravioletmore » region of 100–200 nm, and the maximum absorption intensity is ~100 times that in the visible region. Further, the optical responses to doping in the Si clusters were studied.« less

Theoretical Prediction of Si 2–Si 33 Absorption Spectra

DOE PAGES

Zhao, Li -Zhen; Lu, Wen -Cai; Qin, Wei; ...

2017-07-07

Here, the optical absorption spectra of Si 2–Si 33 clusters were systematically studied by a time-dependent density functional theory approach. The calculations revealed that the absorption spectrum becomes significantly broad with increasing cluster size, stretching from ultraviolet to the infrared region. The absorption spectra are closely related to the structural motifs. With increasing cluster size, the absorption intensity of cage structures gradually increases, but the absorption curves of the prolate and the Y-shaped structures are very sensitive to cluster size. If the transition energy reaches ~12 eV, it is noted that all the clusters have remarkable absorption in deep ultravioletmore » region of 100–200 nm, and the maximum absorption intensity is ~100 times that in the visible region. Further, the optical responses to doping in the Si clusters were studied.« less

Absorption line indices in the UV. I. Empirical and theoretical stellar population models

NASA Astrophysics Data System (ADS)

Maraston, C.; Nieves Colmenárez, L.; Bender, R.; Thomas, D.

2009-01-01

Aims: Stellar absorption lines in the optical (e.g. the Lick system) have been extensively studied and constitute an important stellar population diagnostic for galaxies in the local universe and up to moderate redshifts. Proceeding towards higher look-back times, galaxies are younger and the ultraviolet becomes the relevant spectral region where the dominant stellar populations shine. A comprehensive study of ultraviolet absorption lines of stellar population models is however still lacking. With this in mind, we study absorption line indices in the far and mid-ultraviolet in order to determine age and metallicity indicators for UV-bright stellar populations in the local universe as well as at high redshift. Methods: We explore empirical and theoretical spectral libraries and use evolutionary population synthesis to compute synthetic line indices of stellar population models. From the empirical side, we exploit the IUE-low resolution library of stellar spectra and system of absorption lines, from which we derive analytical functions (fitting functions) describing the strength of stellar line indices as a function of gravity, temperature and metallicity. The fitting functions are entered into an evolutionary population synthesis code in order to compute the integrated line indices of stellar populations models. The same line indices are also directly evaluated on theoretical spectral energy distributions of stellar population models based on Kurucz high-resolution synthetic spectra, In order to select indices that can be used as age and/or metallicity indicators for distant galaxies and globular clusters, we compare the models to data of template globular clusters from the Magellanic Clouds with independently known ages and metallicities. Results: We provide synthetic line indices in the wavelength range ~1200 Å to ~3000 Å for stellar populations of various ages and metallicities.This adds several new indices to the already well-studied CIV and SiIV absorptions. Based on the comparison with globular cluster data, we select a set of 11 indices blueward of the 2000 Å rest-frame that allows us to recover well the ages and the metallicities of the clusters. These indices are ideal to study ages and metallicities of young galaxies at high redshift. We also provide the synthetic high-resolution stellar population SEDs.

Detection of Ne VIII in an Intervening Multiphase Absorption System Toward 3C 263

NASA Astrophysics Data System (ADS)

Narayanan, Anand; Wakker, Bart P.; Savage, Blair D.

2009-09-01

We report the detection of Ne VIII in an intervening multiphase absorption line system at z = 0.32566 in the Far Ultraviolet Spectroscopic Explorer spectrum of the quasar 3C 263 (zem = 0.646). The Ne VIII λ770 Å detection has a 3.9σ significance. At the same velocity, we also find absorption lines from C IV, O III, O IV, and N IV. The line parameter measurements yield log [N(Ne VIII) cm-2] = 13.98+0.10 -0.13 and b = 49.8 ± 5.5 km s-1. We find that the ionization mechanism in the gas phase giving rise to the Ne VIII absorption is inconsistent with photoionization. The absorber has a multiphase structure, with the intermediate ions produced in cool photoionized gas and the Ne VIII most likely in a warm collisionally ionized medium in the temperature range (0.5-1.0) × 106 K. This is the second ever detection of an intervening Ne VIII absorption system. Its properties resemble the previous Ne VIII absorber reported by Savage and colleagues. Direct observations of H I and O VI are needed to better constrain the physical conditions in the collisionally ionized gas phase of this absorber. Based on observations with the NASA-CNES-CSA Far Ultraviolet Spectroscopic Explorer operated by Johns Hopkins University, supported by NASA contract NAS5-32985.

Fiscal Year 2011 Director’s Strategic Initiative Final Report Heterogeneous Device Architectures Incorporating Nitride Semiconductors for Enhanced Functionality of Optoelectronic Devices

DTIC Science & Technology

2014-03-01

electromagnetic radiation across the spectrum from the ultraviolet ( UV ) to terahertz, heterogeneous integration of these materials with others having different...weak absorption that limit the QE of homogenous SiC-based photodetectors in the deep UV and near UV regions, respectively. Furthermore, we have...Polarization-Enhanced III-Nitride-SiC Avalanche Photodiodes Semiconductor-based ultraviolet ( UV ) avalanche photodetectors (APDs) have significant promise

Effects of iron on optical properties of dissolved organic matter.

PubMed

Poulin, Brett A; Ryan, Joseph N; Aiken, George R

2014-09-02

Iron is a source of interference in the spectroscopic analysis of dissolved organic matter (DOM); however, its effects on commonly employed ultraviolet and visible (UV-vis) light adsorption and fluorescence measurements are poorly defined. Here, we describe the effects of iron(II) and iron(III) on the UV-vis absorption and fluorescence of solutions containing two DOM fractions and two surface water samples. In each case, regardless of DOM composition, UV-vis absorption increased linearly with increasing iron(III). Correction factors were derived using iron(III) absorption coefficients determined at wavelengths commonly used to characterize DOM. Iron(III) addition increased specific UV absorbances (SUVA) and decreased the absorption ratios (E2:E3) and spectral slope ratios (SR) of DOM samples. Both iron(II) and iron(III) quenched DOM fluorescence at pH 6.7. The degree and region of fluorescence quenching varied with the iron:DOC concentration ratio, DOM composition, and pH. Regions of the fluorescence spectra associated with greater DOM conjugation were more susceptible to iron quenching, and DOM fluorescence indices were sensitive to the presence of both forms of iron. Analyses of the excitation-emission matrices using a 7- and 13-component parallel factor analysis (PARAFAC) model showed low PARAFAC sensitivity to iron addition.

Effects of iron on optical properties of dissolved organic matter

USGS Publications Warehouse

Poulin, Brett; Ryan, Joseph N.; Aiken, George R.

2014-01-01

Iron is a source of interference in the spectroscopic analysis of dissolved organic matter (DOM); however, its effects on commonly employed ultraviolet and visible (UV–vis) light adsorption and fluorescence measurements are poorly defined. Here, we describe the effects of iron(II) and iron(III) on the UV–vis absorption and fluorescence of solutions containing two DOM fractions and two surface water samples. In each case, regardless of DOM composition, UV–vis absorption increased linearly with increasing iron(III). Correction factors were derived using iron(III) absorption coefficients determined at wavelengths commonly used to characterize DOM. Iron(III) addition increased specific UV absorbances (SUVA) and decreased the absorption ratios (E2:E3) and spectral slope ratios (SR) of DOM samples. Both iron(II) and iron(III) quenched DOM fluorescence at pH 6.7. The degree and region of fluorescence quenching varied with the iron:DOC concentration ratio, DOM composition, and pH. Regions of the fluorescence spectra associated with greater DOM conjugation were more susceptible to iron quenching, and DOM fluorescence indices were sensitive to the presence of both forms of iron. Analyses of the excitation–emission matrices using a 7- and 13-component parallel factor analysis (PARAFAC) model showed low PARAFAC sensitivity to iron addition.

Visualization under ultraviolet light enhances 100-fold the sensitivity of peroxidase-stained blots.

PubMed

Domingo, A; Marco, R

1989-10-01

As described in this article, visualization and/or photography under uv light of 4-chloro-1-naphthol-developed, peroxidase-marked immunoblots allows an increase in sensitivity of more than 100 times over the apparent staining results observable under normal visible white light. This increase in sensitivity can be obtained with the minimal additional requirement of an uv lamp, with the actual chloronaphthol staining procedure remaining unaltered and thereby allowing the monitoring of specific reactions with much smaller quantities of antigen or antibodies. Substantial shortening of the procedure is another advantage, making it possible to complete in 20 min or even less a procedure usually requiring 3 to 6 h. The phenomenon depends on the uv absorption and the fluorescence quenching properties of the products of the peroxidase reaction. The absorption spectra of the membranes with or without peroxidase products indicate that an intermediate in the peroxidase reaction is responsible for the absorption under uv light. This intermediate accumulates under conditions where the final product absorbing in the visible light has not begun to be produced, thus explaining the large increase in sensitivity. The behaviors of three types of membranes, nitrocellulose, nylon, and Immobilon (PVDF), are compared. Due to its lower uv absorption, PVDF gives by far the best results, followed by nitrocellulose.

Total internal reflection-based side-pumping configuration for terawatt ultraviolet amplifier and laser oscillator development

NASA Astrophysics Data System (ADS)

Cadatal-Raduban, Marilou; Pham, Minh Hong; Pham, Duong Van; Bui, Duong Thi Thuy; Yamanoi, Kohei; Takeda, Kohei; Empizo, Melvin John F.; Mui, Luong Viet; Shimizu, Toshihiko; Nguyen, Hung Dai; Sarukura, Nobuhiko; Fukuda, Tsuguo

2018-06-01

A two-side-pumping scheme that is based on total internal reflection in a diamond-cut Ce3+:LiCaAlF6 crystal suitable for the development of an ultraviolet laser and femtosecond amplifier system is proposed. Experimental fluorescence images and lasing results that demonstrate total internal reflection of the excitation beam using this diamond-cut crystal are presented. Calculations for the optimized crystal geometry that facilitate high extraction efficiency and homogeneity of the absorbed excitation beam are also discussed. About 50% increase in extraction efficiency compared to previously reported chirped-pulse femtosecond ultraviolet amplifier operating at 50-GW peak power is expected using this total internal reflection-based two-side-pumping configuration and a diamond-cut Ce3+:LiCaAlF6 crystal with a geometry of {φ _1} = 103°, {φ _2} = {φ _4} = 82°, {φ _3} = 93°, a length of 1.23 cm, a height of 2 cm, and an absorption coefficient of 1.5 cm-1. Our results can be used as a guide during the crystal growth process by providing the appropriate crystal geometry and size for a particular absorption coefficient to achieve high extraction efficiency. With the appropriate crystal combined with multiple-beam pumping afforded by the side-pumping scheme, the development of an all-solid-state ultraviolet laser operating at terawatt level would be within reach.

Particle sizes and composition of Mars atmospheric dust based upon Viking and Mariner 9 observations

NASA Technical Reports Server (NTRS)

Clancy, R. T.; Lee, S. W.; Gladstone, G. R.

1993-01-01

Mars atmospheric dust can play an important role in the thermal structure of the Mars atmosphere during periods of high dust loading. However, the radiative properties of Mars atmospheric dust remain uncertain due to uncertain definitions of the dust composition and size distribution. The analysis by Toon et al., of Mariner 9 IRIS spectra during the 1971-1972 global dust storm indicated a reasonable match between the modeled 9-micron absorption of montmorillinite and the observed 9-micron absorption. Toon et al. also determined that an effective (cross-section weighted) mean radius of 2.5 microns (R(sub mode) = 0.4 microns) provided a consistent fit of montmorillinite to the IRIS dust spectra at 9 microns. Pollack et al. analyzed Viking lander observations of atmospheric extinction and scattering at visible-near IR wavelengths (0.5-1.0 microns), and obtained consistency with the Toon et al. dust size distribution when the effects of nonspherical particle shapes were included. An additional, minor (1 percent) component of visible-ultraviolet absorbing material was required to model the derived visible (0.86) and ultraviolet (0.4-0.6) single-scattering albedos of the dust, since montmorillinite does not absorb sufficiently in this wavelength region. A combined analysis of the Viking IRTM and Mariner 9 observations was conducted to reassess the model of Mars atmospheric ultraviolet-to-infrared measurements of dust absorption and scattering. The optical constants for palagonite are incorporated in a doubling-adding radiative transfer model of the Mars atmosphere to simulate Mariner 9 IRIS spectra as well as the Viking IRTM IR band observations. Visible and ultraviolet single-scattering albedos based on the Hansen and Travis Mie scattering code were also derived. A tentative conclusion is that smaller dust particles (R(sub mode) = 0.15 microns, cross-section weighted mean R = 1.2 microns) composed of palagonite provide a much improved fit to the Mariner 9 IRIS spectra; agreement with the observed ratio of visible-to-infrared extinction opacities; and ultraviolet and visible single-scattering albedos comparable to their observed values.

Could G Asteroids be the Parent Bodies of the CM Chondrites?

NASA Astrophysics Data System (ADS)

Burbine, T. H.; Binzel, R. P.

1995-09-01

Since almost all meteorites are believed to be derived from asteroidal source bodies, the comparison of asteroid and meteorite spectra should allow for possible meteorite parent bodies to be identified. However only two asteroids with unique spectral characteristics, 4 Vesta with the basaltic achondrites [1] and near-Earth asteroid 3103 Eger with the aubrites [2], have been convincingly linked with any meteorite type. Farinella et al. [3] has done a study of 2355 numbered main-belt asteroids to determine which asteroids have the highest probability of having their fragments injected into the 3:1 mean motion and the nu6 secular resonance regions. Interestingly, asteroids with the third (19 Fortuna), tenth (1 Ceres) and eleventh (13 Egeria) highest theoretical total fragment delivery efficiencies are G-asteroids, a moderately rare type of asteroid with approximately ten known members. (Vesta has the fifth highest theoretical total fragment delivery efficiency.) G-asteroids tend to have the strongest ultraviolet, 0.7 micrometers and 3 micrometers absorption features of all C-type (B, C, F and G) asteroids, appearing to indicate that G-asteroids are at the upper range of the aqueous alteration sequence in the asteroid population. (The 0.7 micrometers feature is apparently due to iron oxides in hydrated silicates and the 3 micrometers feature is apparently due to hydrated minerals.) Meteorites that have reflectance spectra with a 3 micrometers feature of comparable intensity to those of the G-asteroids are the CI, CM and CR chondrites. However, G-asteroids (like all C-types) have ultraviolet absorption features that are weaker than previously measured meteorite spectra. Comparisons of reflectance spectra between Ceres and meteorite samples appear to indicate that Ceres is compositionally different from almost all known carbonaceous chondrites. Both Fortuna and Egeria have an absorption feature centered around 0.7 micrometers [4] that is similar in structure and strength to those found in many CM chondrites. The visible and near-infrared spectrum of Fortuna [5] matches very well the spectra of CM chondrites Murchison (bulk powder) [6] and LEW90500 (particle sizes less than 100 micrometers) [7]. However, the ultraviolet absorption feature is still weaker in Fortuna's spectrum. A spectrum of a bulk powder of LEW90500 does have an ultraviolet feature that matches Fortuna's feature, but this spectrum is substantially bluer than Fortuna in the near-infrared. Egeria's ultraviolet absorption feature also matches very well the ultraviolet feature in LEW90500Us (bulk powder) spectrum, but this spectrum is slightly redder than Egeria [5] in the near-infrared. The question is how unique is any postulated linkage between the CM chondrites and the G-asteroids. The problem is that approximately two-thirds of all C-type asteroids have 3 micrometers absorption features [8] and approximately three-fourths have 0.7 micrometers absorption features [4]. However of all observed C-type asteroids, Fortuna and Egeria appear to be two of the best spectral matches for the CM chondrites. Coupled with the high probability that these two asteroids are injecting large numbers of fragments into meteorite-supplying resonances, G-asteroids Fortuna and Egeria appear to be possible CM chondrite parent bodies. Acknowledgments: This research is supported by NASA Grant Number NAGW-2049. References: [1] Binzel R. P. and Xu S. (1993) Science, 260, 186-191. [2] Gaffey M. J. et al. (1992) Icarus, 100, 95-109. [3] Farinella P. et al. (1993) Icarus, 101, 174-187. [4] Sawyer S. R. (1991) Ph.D. thesis, Univ. of Texas, Austin. [5] Bell J. F. et al. (1988) LPS XIX, 57-58. [6] Gaffey M. J. (1976) JGR, 81, 905-920. [7] Hiroi T. et al. (1993) Science, 261, 1016-1018. [8] Jones T. D. et al. (1990) Icarus, 88,172-192.

The development of a tunable, single-frequency ultraviolet laser source for UV filtered Rayleigh scattering

NASA Technical Reports Server (NTRS)

Finkelstein, N.; Gambogi, J.; Lempert, Walter R.; Miles, Richard B.; Rines, G. A.; Finch, A.; Schwarz, R. A.

1995-01-01

We present the development of a flexible, high power, narrow line width, tunable ultraviolet source for diagnostic application. By frequency tripling the output of a pulsed titanium-sapphire laser, we achieve broadly tunable (227-360 nm) ultraviolet light with high quality spatial and spectral resolution. We also present the characterization of a mercury vapor cell which provides a narrow band, sharp edge absorption filter at 253.7 nm. These two components form the basis for the extension of the Filtered Rayleigh Scattering technique into the ultraviolet. The UV-FRS system is comprised of four pieces: a single frequency, cw tunable Ti:Sapphire seeding source; a high-powered pulsed Ti:Sapphire oscillator; a third harmonic generator system; and an atomic mercury vapor filter. In this paper we discuss the development and characterization of each of these elements.

Ultraviolet Spectra of Two Magnetic White Dwarfs and Ultraviolet Spectra of Subluminous Objects Found in the Kiso Schmidt Survey

NASA Technical Reports Server (NTRS)

Wegner, Gary A.

1987-01-01

Low resolution International Ultraviolet Explorer (IUE) spectroscopic observations of two magnetic white dwarfs BPM25114 and K813-14 were obtained using both the SWP and LWP cameras. The first object has an observed magnetic field of 4 x 10(7) Gauss and the second has one of 3 x 10(7) Gauss. Both objects have overall spectral energy distributions appropriate for cool DA white dwarfs with T(eff) near 10,000 K and accordingly show strong lambda lambda 1400 and 1600 absorption in their spectra. Compared to non-magnetic DA white dwarfs of comparable effective temperature, there are some differences in the profiles, presumably produced by the magnetic fields in these objects. In addition, the ultraviolet spectra of a number of hot subluminous stars in the Kiso Schmidt survey were observed.

The Meselson-Stahl Experiment

ERIC Educational Resources Information Center

Szeberenyi, Jozsef

2012-01-01

Terms to be familiar with before you start to solve the test: DNA replication, nitrogen isotopes, density labeling, cesium chloride density gradient centrifugation, ultraviolet absorption, DNA denaturation, circular and linear DNA, superspiralization, superhelical DNA, and template.

Variability in Chemical Vapor Deposited Zinc Sulfide: Assessment of Legacy and International CVD ZnS Materials

DOE Office of Scientific and Technical Information (OSTI.GOV)

McCloy, John S.; Korenstein, Ralph

2009-10-06

Samples of CVD ZnS from the United States, Germany, Israel, and China were evaluated using transmission spectroscopy, x-ray diffraction, photoluminescence, and biaxial flexure testing. Visible and near-infrared scattering, 6 μm absorption, and ultraviolet cut-on edge varied substantially in tested materials. Crystallographic hexagonality and texture was determined and correlated with optical scattering. Transmission cut-on (ultraviolet edge) blue-shifts with annealing and corresponds to visible color but not the 6 μm absorption. Photoluminescence results suggest that CVD ZnS exhibits a complex suite of electronic bandgap defects. All CVD ZnS tested with biaxial flexure exhibit similar fracture strength values and Weibull moduli. This surveymore » suggests that technical understanding of the structure and optical properties CVD ZnS is still in its infancy.« less

Chemical Constitution of the Host-Specific Toxin of Helminthosporium carbonum1

PubMed Central

Pringle, Ross B.

1970-01-01

The host-specific toxin of Helminthosporium carbonum Ullstrup has a molecular formula approximating C32H50N6O10. The compound has been crystallized and a crystalline hydrochloride derivative has been produced. The molecular weight, as determined by chromatography on Sephadex G-10, is slightly less than 700. The toxin appears to be a cyclic peptide, since, although it does not react with ninhydrin or dinitrofluorobenzene, it yields, on hydrolysis, compounds which react to these reagents. It is unstable in dilute acids, yielding ninhydrin-reacting products. Complete acid hydrolysis yields alanine, proline, and three other ninhydrin-reacting components. The infrared spectrum of the toxin reveals an ester band in addition to amide absorption. Its ultraviolet spectrum reveals the presence of unsaturation in the molecule. The toxin is relatively unstable and loses its specific toxicity. This loss of activity appears to be associated with loss of nitrogen and with decreased solubility in water. PMID:5481091

Chemical constitution of the host-specific toxin of Helminthosporium carbonum.

PubMed

Pringle, R B

1970-07-01

The host-specific toxin of Helminthosporium carbonum Ullstrup has a molecular formula approximating C(32)H(50)N(6)O(10). The compound has been crystallized and a crystalline hydrochloride derivative has been produced. The molecular weight, as determined by chromatography on Sephadex G-10, is slightly less than 700. The toxin appears to be a cyclic peptide, since, although it does not react with ninhydrin or dinitrofluorobenzene, it yields, on hydrolysis, compounds which react to these reagents. It is unstable in dilute acids, yielding ninhydrin-reacting products. Complete acid hydrolysis yields alanine, proline, and three other ninhydrin-reacting components. The infrared spectrum of the toxin reveals an ester band in addition to amide absorption. Its ultraviolet spectrum reveals the presence of unsaturation in the molecule. The toxin is relatively unstable and loses its specific toxicity. This loss of activity appears to be associated with loss of nitrogen and with decreased solubility in water.

THE NISSL SUBSTANCE OF LIVING AND FIXED SPINAL GANGLION CELLS

PubMed Central

Deitch, Arline D.; Moses, Montrose J.

1957-01-01

Living chick spinal ganglion neurons grown for 19 to 25 days in vitro were photographed with a color-translating ultraviolet microscope (UV-91) at 265, 287, and 310 mµ. This instrument was unique in permitting rapid accumulation of ultraviolet information with minimal damage to the cell. In the photographs taken at 265 mµ of the living neurons, discrete ultraviolet-absorbing cytoplasmic masses were observed which were found to be virtually unchanged in appearance after formalin fixation. These were identical with the Nissl bodies of the same cells seen after staining with basic dyes. The correlation of ultraviolet absorption, ribonuclease extraction, and staining experiments with acid and basic dyes confirmed the ribonucleoprotein nature of these Nissl bodies in the living and fixed cells. No change in distribution or concentration of ultraviolet-absorbing substance was observed in the first 12 ultraviolet photographs of a neuron, and it is concluded that the cells had not been subjected to significant ultraviolet damage during the period of photography. On the basis of these observations, as well as previous findings with phase contrast microscopy, it is concluded that Nissl bodies preexist in the living neuron as discrete aggregates containing high concentrations of nucleoprotein. PMID:13438929

Fusion of Ultraviolet-Visible and Infrared Transient Absorption Spectroscopy Data to Model Ultrafast Photoisomerization.

PubMed

Debus, Bruno; Orio, Maylis; Rehault, Julien; Burdzinski, Gotard; Ruckebusch, Cyril; Sliwa, Michel

2017-08-03

Ultrafast photoisomerization reactions generally start at a higher excited state with excess of internal vibrational energy and occur via conical intersections. This leads to ultrafast dynamics which are difficult to investigate with a single transient absorption spectroscopy technique, be it in the ultraviolet-visible (UV-vis) or infrared (IR) domain. On one hand, the information available in the UV-vis domain is limited as only slight spectral changes are observed for different isomers. On the other hand, the interpretation of vibrational spectra is strongly hindered by intramolecular relaxation and vibrational cooling. These limitations can be circumvented by fusing UV-vis and IR transient absorption spectroscopy data in a multiset multivariate curve resolution analysis. We apply this approach to describe the spectrodynamics of the ultrafast cis-trans photoisomerization around the C-N double bond observed for aromatic Schiff bases. Twisted intermediate states could be elucidated, and isomerization was shown to occur through a continuous complete rotation. More broadly, data fusion can be used to rationalize a vast range of ultrafast photoisomerization processes of interest in photochemistry.

Line identifications, line strengths, and continuum flux measurements in the ultraviolet spectrum of Arcturus

NASA Technical Reports Server (NTRS)

Carpenter, K. G.; Wing, R. F.; Stencel, R. E.

1985-01-01

The ultraviolet spectrum of Arcturus has been observed at high resolution with the IUE satellite. Line identifications, mean absolute 'continuum' flux measurements, integrated absolute emission-line fluxes, and measurements of selected absorption line strengths are presented for the 2250-2930 A region. In the 1150-2000 A region, identifications are given primarily on the basis of low-resolution spectra. Chromospheric emission lines have been identified with low-excitation species including H I, C I, C II, O I, Mg I, Mg II, Al II, Si I, Si II, S I, and Fe II; there is no evidence for lines of C IV, N V, or other species requiring high temperatures. A search for molecular absorption features in the 2500-2930 A interval has led to several tentative identifications, but only OH could be established as definitely present. Iron lines strongly dominate the identifications in the 2250-2930 A region, Fe II accounting for about 86 percent of the emission features and Fe I for 43 percent of the identified absorption features.

Measurement of the vacuum-ultraviolet absorption spectrum of low-k dielectrics using X-ray reflectivity

NASA Astrophysics Data System (ADS)

Choudhury, F. A.; Nguyen, H. M.; King, S. W.; Lee, C. H.; Lin, Y. H.; Fung, H. S.; Chen, C. C.; Li, W.; Benjamin, D.; Blatz, J. M.; Nishi, Y.; Shohet, J. L.

2018-02-01

During plasma processing, low-k dielectrics are exposed to high levels of vacuum ultraviolet (VUV) radiation that can cause severe damage to dielectric materials. The degree and nature of VUV-induced damage depend on the VUV photon energies and fluence. In this work, we examine the VUV-absorption spectrum of low-k organosilicate glass using specular X-ray reflectivity (XRR). Low-k SiCOH films were exposed to synchrotron VUV radiation with energies ranging from 7 to 21 eV, and the density vs. depth profile of the VUV-irradiated films was extracted from fitting the XRR experimental data. The results show that the depth of the VUV-induced damage layer is a function of the photon energy. Between 7 and 11 eV, the depth of the damaged layer decreases sharply from 110 nm to 60 nm and then gradually increases to 85 nm at 21 eV. The maximum VUV absorption in low-k films occurs between 11 and 15 eV. The depth of the damaged layer was found to increase with film porosity.

CR-39 (PADC) Reflection and Transmission of Light in the Ultraviolet-Near-Infrared (UV-NIR) Range.

PubMed

Traynor, Nathan B J; McLauchlin, Christopher; Dodge, Kenneth; McGarrah, James E; Padalino, Stephen J; McCluskey, Michelle; Sangster, T C; McLean, James G

2018-04-01

The spectral reflection (specular and diffuse) and transmission of Columbia Resin 39 (CR-39) were measured for incoherent light with wavelengths in the range of 200-2500 nm. These results will be of use for the optical characterization of CR-39, as well as in investigations of the chemical modifications of the polymer caused by ultraviolet (UV) exposure. A Varian Cary 5000 was used to perform spectroscopy on several different thicknesses of CR-39. With proper analysis for the interdependence of reflectance and transmittance, results are consistent across all samples. The reflectivity from each CR-39-air boundary reveals an increase in the index of refraction in the near-UV. Absorption observations are consistent with the Beer-Lambert law. Strong absorption of UV light of wavelength shorter than 350 nm suggests an optical band gap of 3.5 eV, although the standard analysis is not conclusive. Absorption features observed in the near infrared are assigned to molecular vibrations, including some that are new to the literature.

Ultraviolet, X-ray, and infrared observations of HDE 226868 equals Cygnus X-1

NASA Technical Reports Server (NTRS)

Treves, A.; Chiappetti, L.; Tanzi, E. G.; Tarenghi, M.; Gursky, H.; Dupree, A. K.; Hartmann, L. W.; Raymond, J.; Davis, R. J.; Black, J.

1980-01-01

During April, May, and July of 1978, HDE 226868, the optical counterpart of Cygnus X-1, was repeatedly observed in the ultraviolet with the IUE satellite. Some X-ray and infrared observations have been made during the same period. The general shape of the spectrum is that expected from a late O supergiant. Strong absorption features are apparent in the ultraviolet, some of which have been identified. The equivalent widths of the most prominent lines appear to be modulated with the orbital phase. This modulation is discussed in terms of the ionization contours calculated by Hatchett and McCray, for a binary X-ray source in the stellar wind of the companion.

Photocurrent enhancement mechanisms in bilayer nanofilm-based ultraviolet photodetectors made from ZnO and ZnS spherical nanoshells

PubMed Central

2014-01-01

Hollow-sphere bilayer nanofilm-based ultraviolet light photodetectors made from ZnO and ZnS spherical nanoshells show enhanced photocurrent, which are comparable to or even better than those of other semiconductor nanostructures with different shapes. In this work, the photocurrent enhancement mechanisms of these bilayer nanofilm-based ultraviolet light photodetectors are explained, which could be attributed to the strong light absorption based on the whispering gallery mode resonances, the separation of the photogenerated carriers through the internal electric field within the bilayer nanofilms, the hopping-like electrical transport, and the effective charge injection from Cr/Au contacts to the nanofilms. PMID:25136287

Hourly variations in O VI P Cygni profiles of hot stars

NASA Technical Reports Server (NTRS)

York, D. G.; Vidal-Madjar, A.; Laurent, C.; Bonnet, R.

1977-01-01

Significant changes in the ultraviolet absorption profiles are reported in the spectra of Delta Ori A, Iota Ori, and Zeta Pup. The present data show changes in count rates in excess of 30 per cent at velocities more negative than -900 km/s, if these data are interpreted as being dominated by O VI absorption in stellar winds. The time scales range from 1 to 6 hours.

Simulation based comparative analysis of photoresponse in front- and back-illuminated GaN P-I-N ultraviolet photodetectors

NASA Astrophysics Data System (ADS)

Wang, Jun; Guo, Jin; Xie, Feng; Wang, Guosheng; Wu, Haoran; Song, Man; Yi, Yuanyuan

2016-10-01

This paper presents the comparative analysis of influence of doping level and doping profile of the active region on zero bias photoresponse characteristics of GaN-based p-i-n ultraviolet (UV) photodetectors operating at front- and back-illuminated. A two dimensional physically-based computer simulation of GaN-based p-i-n UV photodetectors is presented. We implemented GaN material properties and physical models taken from the literature. It is shown that absorption layer doping profile has notable impacts on the photoresponse of the device. Especially, the effect of doping concentration and distribution of the absorption layer on photoresponse is discussed in detail. In the case of front illumination, comparative to uniform n-type doping, the device with n-type Gaussian doping profiles at absorption layer has higher responsivity. Comparative to front illumination, back illuminated detector with p-type doping profiles at absorption layer has higher maximum photoresponse, while the Gaussian doping profiles have a weaker ability to enhance the device responsivity. It is demonstrated that electric field distribution, mobility degradation, and recombinations are jointly responsible for the variance of photoresponse. Our work enriches the understanding and utilization of GaN based p-i-n UV photodetectors.

Ionospheric-thermospheric UV tomography: 2. Comparison with incoherent scatter radar measurements

NASA Astrophysics Data System (ADS)

Dymond, K. F.; Nicholas, A. C.; Budzien, S. A.; Stephan, A. W.; Coker, C.; Hei, M. A.; Groves, K. M.

2017-03-01

The Special Sensor Ultraviolet Limb Imager (SSULI) instruments are ultraviolet limb scanning sensors that fly on the Defense Meteorological Satellite Program F16-F19 satellites. The SSULIs cover the 80-170 nm wavelength range which contains emissions at 91 and 136 nm, which are produced by radiative recombination of the ionosphere. We invert the 91.1 nm emission tomographically using a newly developed algorithm that includes optical depth effects due to pure absorption and resonant scattering. We present the details of our approach including how the optimal altitude and along-track sampling were determined and the newly developed approach we are using for regularizing the SSULI tomographic inversions. Finally, we conclude with validations of the SSULI inversions against Advanced Research Project Agency Long-range Tracking and Identification Radar (ALTAIR) incoherent scatter radar measurements and demonstrate excellent agreement between the measurements. As part of this study, we include the effects of pure absorption by O2, N2, and O in the inversions and find that best agreement between the ALTAIR and SSULI measurements is obtained when only O2 and O are included, but the agreement degrades when N2 absorption is included. This suggests that the absorption cross section of N2 needs to be reinvestigated near 91.1 nm wavelengths.

The low-iron, reduced surface of Mercury as seen in spectral reflectance by MESSENGER

NASA Astrophysics Data System (ADS)

Izenberg, Noam R.; Klima, Rachel L.; Murchie, Scott L.; Blewett, David T.; Holsclaw, Gregory M.; McClintock, William E.; Malaret, Erick; Mauceri, Calogero; Vilas, Faith; Sprague, Ann L.; Helbert, Jörn; Domingue, Deborah L.; Head, James W.; Goudge, Timothy A.; Solomon, Sean C.; Hibbitts, Charles A.; Dyar, M. Darby

2014-01-01

The MESSENGER spacecraft's Mercury Atmospheric and Surface Composition Spectrometer (MASCS) obtained more than 1.6 million reflectance spectra of Mercury's surface from near-ultraviolet to near-infrared wavelengths during the first year of orbital operations. A global analysis of spectra in the wavelength range 300-1450 nm shows little regional variation in absolute reflectance or spectral slopes and a lack of mineralogically diagnostic absorptions. In particular, reflectance spectra show no clear evidence for an absorption band centered near 1 μm that would be associated with the presence of ferrous iron in silicates. There is, however, evidence for an ultraviolet absorption possibly consistent with a very low iron content (2-3 wt% FeO or less) in surface silicates and for the presence of small amounts of metallic iron or other opaque minerals in the form of nano- or micrometer-sized particles. These findings are consistent with MESSENGER X-ray and gamma-ray measurements of Mercury's surface iron abundance. Although X-ray and gamma-ray observations indicate higher than expected quantities of sulfur on the surface, reflectance spectra show no absorption bands diagnostic of sulfide minerals. Whereas there is strong evidence of water ice in permanently shadowed craters near Mercury's poles, MASCS spectra provide no evidence for hydroxylated materials near permanently shadowed craters.

[Using ultraviolet-visible ( UV-Vis) absorption spectrum to estimate the dissolved organic matter (DOM) concentration in water, soils and sediments of typical water-level fluctuation zones of the Three Gorges Reservoir areas].

PubMed

Li, Lu-lu; Jiang, Tao; Lu, Song; Yan, Jin-long; Gao, Jie; Wei, Shi-qiang; Wang, Ding-yong; Guo, Nian; Zhao, Zhena

2014-09-01

Dissolved organic matter (DOM) is a very important component in terrestrial ecosystem. Chromophoric dissolved organic matter (CDOM) is a significant constituent of DOM, which can be measured by ultraviolet-visible (UV-Vis) absorption spectrum. Thus the relationship between CDOM and DOM was investigated and established by several types of models including single-wavelength model, double-wavelength model, absorption spectrum slope (S value) model and three-wavelength model, based on the UV-Vis absorption coefficients of soil and sediment samples (sampled in July of 2012) and water samples (sampled in November of 2012) respectively. The results suggested that the three-wavelength model was the best for fitting, and the determination coefficients of water, soil and sediment data were 0. 788, 0. 933 and 0. 856, respectively. Meanwhile, the nominal best model was validated with the UV-Vis data of 32 soil samples and 36 water samples randomly collected in 2013, showing the RRMSE and MRE were 16. 5% and 16. 9% respectively for soil DOM samples, 10. 32% and 9. 06% respectively for water DOM samples, which further suggested the prediction accuracy was higher in water DOM samples as compared with that in soil DOM samples.

Activated mineral powders for asphalt concrete mixture

NASA Astrophysics Data System (ADS)

Kuznetsov, D. A.; Lukash, E. A.

2018-03-01

Possibilities of activation of disperse mineral powders from the technogenic raw materials of KMA by ultraviolet irradiation are considered in this article. The optimum time of ultraviolet exposure for each material is determined during which the concentration of exchange centers is increased, the rate of rehydration is slowed down and the moisture absorption is significantly reduced. It is shown that both physical and mechanical characteristics, as well as durability of asphalt concrete prepared on the basis of modified mineral powders are significantly increased.

Variation in the Humification Degree of Dissolved Organic Matter from Cattle Manure during Composting as Analyzed by Ultraviolet-Visible and Fluorescence Spectroscopy.

PubMed

Chen, Yukun; Jiang, Zhao; Zhang, Xiuyuan; Cao, Bo; Yang, Fan; Wang, Ziyi; Zhang, Ying

2017-11-01

This study investigated the degree of humification of dissolved organic matter (DOM) during different periods of cattle manure composting using ultraviolet-visible (UV-vis) and fluorescence spectroscopy (emission, synchronous scan, and excitation-emission matrix) and determined which method is more suitable for analysis of the humification degree of DOM. Two composting piles were prepared by mixing manure and corn straw. One pile (Pile A [PA]) contained inoculated exogenous composite agents at a ratio of 2% (v/v), and a pile without the addition of inoculants (PNA) served as the control treatment. The results showed that ultraviolet integrated absorption intensities in the range of 226 to 400 nm and 260 to 280 nm and specific ultraviolet absorbances at 254 and 280 nm of both PA and PNA gradually increased with composting time. Based on the fluorescence regional integration analysis and parallel factor analysis, the humic-like substances became the main components of the DOM after composting. Our study demonstrated that the humification degree of DOM was enhanced during composting and that the inoculation composite agent was beneficial for the humification of DOM at the mesophilic and thermophilic phases of the composting process. Moreover, the results of correlation analysis and principal component analysis demonstrated that the fluorescence spectral parameters evaluated the humification degree of DOM during the whole cattle manure composting process better than the UV-vis spectral parameters. Copyright © by the American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America, Inc.

Atrazine Molecular Imprinted Polymers: Comparative Analysis by Far-Infrared and Ultraviolet Induced Polymerization

PubMed Central

Chen, Jun; Bai, Lian-Yang; Liu, Kun-Feng; Liu, Run-Qiang; Zhang, Yu-Ping

2014-01-01

Atrazine molecular imprinted polymers (MIPs) were comparatively synthesized using identical polymer formulation by far-infrared (FIR) radiation and ultraviolet (UV)-induced polymerization, respectively. Equilibrium binding experiments were carried out with the prepared MIPs; the results showed that MIPuv possessed specific binding to atrazine compared with their MIPFIR radiation counterparts. Scatchard plot’s of both MIPs indicated that the affinities of the binding sites in MIPs are heterogeneous and can be approximated by two dissociation-constants corresponding to the high-and low-affinity binding sites. Moreover, several common pesticides including atrazine, cyromazine, metamitron, simazine, ametryn, terbutryn were tested to determine their specificity, similar imprinting factor (IF) and different selectivity index (SI) for both MIPs. Physical characterization of the polymers revealed that the different polymerization methods led to slight differences in polymer structures and performance by scanning electron microscope (SEM), Fourier transform infrared absorption (FT-IR), and mercury analyzer (MA). Finally, both MIPs were used as selective sorbents for solid phase extraction (SPE) of atrazine from lake water, followed by high performance liquid chromatography (HPLC) analysis. Compared with commercial C18 SPE sorbent (86.4%–94.8%), higher recoveries of atrazine in spiked lake water were obtained in the range of 90.1%–97.1% and 94.4%–101.9%, for both MIPs, respectively. PMID:24398982

Evolution analysis of EUV radiation from laser-produced tin plasmas based on a radiation hydrodynamics model

PubMed Central

Su, M. G.; Min, Q.; Cao, S. Q.; Sun, D. X.; Hayden, P.; O’Sullivan, G.; Dong, C. Z.

2017-01-01

One of fundamental aims of extreme ultraviolet (EUV) lithography is to maximize brightness or conversion efficiency of laser energy to radiation at specific wavelengths from laser produced plasmas (LPPs) of specific elements for matching to available multilayer optical systems. Tin LPPs have been chosen for operation at a wavelength of 13.5 nm. For an investigation of EUV radiation of laser-produced tin plasmas, it is crucial to study the related atomic processes and their evolution so as to reliably predict the optimum plasma and experimental conditions. Here, we present a simplified radiation hydrodynamic model based on the fluid dynamic equations and the radiative transfer equation to rapidly investigate the evolution of radiation properties and dynamics in laser-produced tin plasmas. The self-absorption features of EUV spectra measured at an angle of 45° to the direction of plasma expansion have been successfully simulated and explained, and the evolution of some parameters, such as the plasma temperature, ion distribution and density, expansion size and velocity, have also been evaluated. Our results should be useful for further understanding of current research on extreme ultraviolet and soft X-ray source development for applications such as lithography, metrology and biological imaging. PMID:28332621

Ultraviolet absorption spectra of shock-heated carbon dioxide and water between 900 and 3050 K

NASA Astrophysics Data System (ADS)

Schulz, C.; Koch, J. D.; Davidson, D. F.; Jeffries, J. B.; Hanson, R. K.

2002-03-01

Spectrally resolved UV absorption cross-sections between 190 and 320 nm were measured in shock-heated CO 2 between 880 and 3050 K and H 2O between 1230 and 2860 K. Absorption spectra were acquired with 10 μs time resolution using a unique kinetic spectrograph, thereby enabling comparisons with time-dependent chemical kinetic modeling of post-shock thermal decomposition and chemical reactions. Although room temperature CO 2 is transparent (σ<10 -22 cm2) at wavelengths longer than 200 nm, hot CO 2 has significant absorption (σ>10 -20 cm2) extending to wavelengths longer than 300 nm. The temperature dependence of CO 2 absorption strongly suggests sharply increased transition probabilities from excited vibrational levels.

The Magellan Evolution of Galaxies Spectroscopic and Ultraviolet Reference Atlas (MegaSaura). II. Stacked Spectra

NASA Astrophysics Data System (ADS)

Rigby, J. R.; Bayliss, M. B.; Chisholm, J.; Bordoloi, R.; Sharon, K.; Gladders, M. D.; Johnson, T.; Paterno-Mahler, R.; Wuyts, E.; Dahle, H.; Acharyya, A.

2018-01-01

We stack the rest-frame ultraviolet spectra of N = 14 highly magnified gravitationally lensed galaxies at redshifts 1.6< z< 3.6. The resulting new composite spans 900< {λ }{rest}< 3000 Å, with a peak signal-to-noise ratio (S/N) of 103 per spectral resolution element (∼100 km s‑1). It is the highest S/N, highest spectral resolution composite spectrum of z ∼ 2–3 galaxies yet published. The composite reveals numerous weak nebular emission lines and stellar photospheric absorption lines that can serve as new physical diagnostics, particularly at high redshift with the James Webb Space Telescope (JWST). We report equivalent widths to aid in proposing for and interpreting JWST spectra. We examine the velocity profiles of strong absorption features in the composite, and in a matched composite of z∼ 0 COS/HST galaxy spectra. We find remarkable similarity in the velocity profiles at z∼ 0 and z∼ 2, suggesting that similar physical processes control the outflows across cosmic time. While the maximum outflow velocity depends strongly on ionization potential, the absorption-weighted mean velocity does not. As such, the bulk of the high-ionization absorption traces the low-ionization gas, with an additional blueshifted absorption tail extending to at least ‑2000 km s‑1. We interpret this tail as arising from the stellar wind and photospheres of massive stars. Starburst99 models are able to replicate this high-velocity absorption tail. However, these theoretical models poorly reproduce several of the photospheric absorption features, indicating that improvements are needed to match observational constraints on the massive stellar content of star-forming galaxies at z∼ 2. We publicly release our composite spectra.

Resonances in the Photoionization Cross Sections of Atomic Nitrogen Shape the Far-ultraviolet Spectrum of the Bright Star in 47 Tucanae

NASA Astrophysics Data System (ADS)

Dixon, William V.; Chayer, Pierre

2013-08-01

The far-ultraviolet spectrum of the Bright Star (B8 III) in 47 Tuc (NGC 104) shows a remarkable pattern: it is well fit by local thermodynamic equilibrium models at wavelengths longer than Lyβ, but at shorter wavelengths it is fainter than the models by a factor of two. A spectrum of this star obtained with the Far Ultraviolet Spectroscopic Explorer shows broad absorption troughs with sharp edges at 995 and 1010 Å and a deep absorption feature at 1072 Å none of which are predicted by the models. We find that these features are caused by resonances in the photoionization cross sections of the first and second excited states of atomic nitrogen (2s 2 2p 3 2 D 0 and 2 P 0). Using cross sections from the Opacity Project, we can reproduce these features, but only if we use the cross sections at their full resolution, rather than the resonance-averaged cross sections usually employed to model stellar atmospheres. These resonances are strongest in stellar atmospheres with enhanced nitrogen and depleted carbon abundances, a pattern typical of post-asymptotic giant branch stars.

Role of HfO 2/SiO 2 thin-film interfaces in near-ultraviolet absorption and pulsed laser damage

DOE PAGES

Papernov, Semyon; Kozlov, Alexei A.; Oliver, James B.; ...

2016-07-15

Here, the role of thin-film interfaces in the near-ultraviolet (near-UV) absorption and pulsed laser-induced damage was studied for ion-beam-sputtered and electron-beam-evaporated coatings comprised from HfO 2 and SiO 2 thin-film pairs. To separate contributions from the bulk of the film and from interfacial areas, absorption and damage threshold measurements were performed for a one-wave (355-nm wavelength) thick, HfO 2 single-layer film and for a film containing seven narrow HfO 2 layers separated by SiO 2 layers. The seven-layer film was designed to have a total optical thickness of HfO 2 layers, equal to one wave at 355 nm and anmore » E-field peak and average intensity similar to a single-layer HfO 2 film. Absorption in both types of films was measured using laser calorimetry and photothermal heterodyne imaging. The results showed a small contribution to total absorption from thin-film interfaces as compared to HfO 2 film material. The relevance of obtained absorption data to coating near-UV, nanosecond-pulse laser damage was verified by measuring the damage threshold and characterizing damage morphology. The results of this study revealed a higher damage resistance in the seven-layer coating as compared to the single-layer HfO 2 film in both sputtered and evaporated coatings. The results are explained through the similarity of interfacial film structure with structure formed during the codeposition of HfO 2 and SiO 2 materials.« less

Ab-initio study of thermodynamic stability, thermoelectric and optical properties of perovskites ATiO3 (A=Pb, Sn)

NASA Astrophysics Data System (ADS)

Noor, N. A.; Mahmood, Q.; Rashid, Muhammad; Ul Haq, Bakhtiar; Laref, A.; Ahmad, S. A.

2018-07-01

The physical behavior of perovskites ATiO3 (A=Pb, Sn) has been explored by using density functional theory based full-potential linearized-augmented-plane-wave plus local-orbital (FP-LAPW+lo) method. The lattice parameters calculated from the optimized structures by using Murnaghan equation of state and Chapin's method have been found in good agreement with the available literature that ensures the reliability of the adopted methodology. Moreover, the optoelectronic and thermoelectric properties have been elaborated by using modified Becke-Johnson exchange potential. The optical behavior has been explored in terms the dielectric constants, refractive indices, absorption spectra and optical loss factors. The absorption spectra of these materials reveal a large absorption in the visible and low ultraviolet part of incident light. The thermoelectric properties of ATiO3 are explained in terms of electrical conductivities, thermal conductivities, power factors, and the specific heat capacities. The ATiO3family of pervoskites has been found to exhibit the bandgaps falling in the visible region of solar spectrum and show high values of thermal efficiency that make them potential multifunctional candidates for optoelectronic and energy harvesting applications.

Near ultraviolet spectroscopic studies of 2,4-diamino-6-piperidinopyrimidine-3-oxide (minoxidil) and 2,4-diamino-6-piperidinopyrimidine (desoxyminoxidil)

NASA Astrophysics Data System (ADS)

Thamann, Thomas J.

The near u.v. spectra of 2,4-diamino-6-piperidinopyrimidine (desoxyminoxidil) and 2,4-diamino-6-piperidinopyrimidine-3-oxide (minoxidil) can be viewed as perturbed pyrimidine spectra. The u.v. properties of pyrimidine and a series of aminopyrimidines, specifically 2,4,6-triaminopyrimidine, are examined to obtain u.v. spectral assignments for desoxyminoxidil and minoxidil. Minoxidil and its desoxy counterpart have C s symmetry, and all π → π* absorptions are allowed 1A' ← 1A' transitions. The two lowest energy π →- π* absorptions observed in minoxidil (262 nm, 292 nm) are tentatively assigned as very mild oxygen → pyrimidine ring charge-transfer transitions. Intensity decreases in protic solvents, and the results of simple Hückel molecular orbital calculations indicate that the 292 nm transition has more charge-transfer character than the 262 nm absorption. The protonated species of desoxyminoxidil and minoxidil have very similar u.v. spectra. This is due to the lack of oxygen-related charge transfer in protonated minoxidil, and the high probability that the positive charge resides in similar environments in the minoxidil and desoxyminoxidil molecular frameworks.

Supersaturation-nucleation behavior of poorly soluble drugs and its impact on the oral absorption of drugs in thermodynamically high-energy forms.

PubMed

Ozaki, Shunsuke; Minamisono, Takuma; Yamashita, Taro; Kato, Takashi; Kushida, Ikuo

2012-01-01

In order to better understand the oral absorption behavior of poorly water-soluble drugs, their supersaturation-nucleation behavior was characterized in fasted state simulated intestinal fluid. The induction time (t(ind)) for nucleation was measured for four model drugs: itraconazole, erlotinib, troglitazone, and PLX4032. Supersaturated solutions were prepared by solvent shift method, and nucleation initiation was monitored by ultraviolet detection. The relationship between t(ind) and degree of supersaturation was analyzed in terms of classical nucleation theory. The defined supersaturation stability proved to be compound specific. Clinical data on oral absorption were investigated for drugs in thermodynamically high-energy forms such as amorphous forms and salts and was compared with in vitro supersaturation-nucleation characteristics. Solubility-limited maximum absorbable dose was proportionate to intestinal effective drug concentrations, which are related to supersaturation stability and thermodynamic solubility. Supersaturation stability was shown to be an important factor in determining the effect of high-energy forms. The characterization of supersaturation-nucleation behavior by the presented method is, therefore, valuable for assessing the potential absorbability of poorly water-soluble drugs. Copyright © 2011 Wiley-Liss, Inc.

A search for ultraviolet circumstellar gas absorption features in alpha Piscis Austrinus (Fomalhaut), a possible Beta Pictoris-like system

NASA Technical Reports Server (NTRS)

Cheng, K.-P.; Bruhweiler, Fred C.; Kondo, Yoji

1994-01-01

Archival high-dispersion International Ultraviolet Explorer (IUE) spectra have been used to search for circumstellar gas absorption features in alpha PsA (A3 V), a nearby (6.7 pc) proto-planetary system candidate. Recent sub-millimeter mapping observations around the region of alpha PsA indicate a spatially resolved dust disk like the one seen around Beta Pic. To determine how closely this putative disk resembles that of Beta Pic, we have searched for signatures of circumstellar gaseous absorption in all the available IUE high-dispersion data of alpha PsA. Examination of co-added IUE spectra shows weak circumstellar absorptions from excited levels in the resonance multiplet of Fe II near 2600 A. We also conclude that the sharp C I feature near 1657 A, previously identified as interstellar absorption toward alpha PsA, likely has a circumstellar origin. However, because the weakness of these absorption features, we will consider the presence of circumstellar gas as tentative and should be verified by using the Goddard High-Resolution Spectrograph aboard the Hubble Space Telescope. No corresponding circumstellar absorption is detected in higher ionization Fe III and Al III. Since the collisionally ionized nonphotospheric Al III resonance absorption seen in Beta Pic is likely formed close to the stellar surface, its absence in the UV spectra of alpha PsA could imply that, in contrast with Beta Pic, there is no active gaseous disk infall onto the central star. In the alpha PsA gaseous disk, if we assume a solar abundance for iron and all the iron is in the form of Fe II, plus a disk temperature of 5000 K, the Fe II UV1 absorption at 2611.8743 A infers a total hydrogen column density along the line of sight through the circumstellar disk of N(H) approximately equals 3.8 x 10(exp 17)/cm.

Ultraviolet and X-ray Variability of the Seyfert 1.5 Galaxy Markarian 817

NASA Astrophysics Data System (ADS)

Winter, Lisa M.; Danforth, Charles; Vasudevan, Ranjan; Brandt, W. N.; Scott, Jennifer; Froning, Cynthia; Keeney, Brian; Shull, J. Michael; Penton, Steve; Mushotzky, Richard; Schneider, Donald P.; Arav, Nahum

2011-02-01

We present an investigation of the ultraviolet and X-ray spectra of the Seyfert 1.5 galaxy Markarian 817. The ultraviolet analysis includes two recent observations taken with the Cosmic Origins Spectrograph (COS) in 2009 August and December, as well as archival spectra from the International Ultraviolet Explorer and the Hubble Space Telescope. Twelve Lyα absorption features are detected in the 1997 Goddard High Resolution Spectrograph (GHRS) and 2009 COS spectra—of these, four are associated with high-velocity clouds in the interstellar medium, four are at low significance, and the remaining four are intrinsic features, which vary between the GHRS and COS observations. The strongest intrinsic absorber in the 1997 spectrum has a systemic velocity of ~-4250 km s-1. The corresponding feature in the COS data is five times weaker than the GHRS absorber. The three additional weak (equivalent width from 13 to 54 mÅ) intrinsic Lyα absorbers are at systemic velocities of -4100 km s-1, -3550 km s-1, and -2600 km s-1. However, intrinsic absorption troughs from highly ionized C IV and N V are not detected in the COS observations. No ionized absorption signatures are detected in the ~14 ks XMM-Newton EPIC spectra. The factor of five change in the intrinsic Lyα absorber is most likely due to bulk motions in the absorber, since there is no drastic change in the UV luminosity of the source from the GHRS to the COS observations. In a study of the variability of Mrk 817, we find that the X-ray luminosity varies by a factor of ~40 over 20 years, while the UV continuum/emission lines vary by at most a factor of ~2.3 over 30 years. The variability of the X-ray luminosity is strongly correlated with the X-ray power-law index, but no correlation is found with the simultaneous optical/UV photometry.

Analysis and design of the ultraviolet warning optical system based on interference imaging

NASA Astrophysics Data System (ADS)

Wang, Wen-cong; Hu, Hui-jun; Jin, Dong-dong; Chu, Xin-bo; Shi, Yu-feng; Song, Juan; Liu, Jin-sheng; Xiao, Ting; Shao, Si-pei

2017-10-01

Ultraviolet warning technology is one of the important methods for missile warning. It provides a very effective way to detect the target for missile approaching alarm. With the development of modern technology, especially the development of information technology at high speed, the ultraviolet early warning system plays an increasingly important role. Compared to infrared warning, the ultraviolet warning has high efficiency and low false alarm rate. In the modern warfare, how to detect the threats earlier, prevent and reduce the attack of precision-guided missile has become a new challenge of missile warning technology. Because the ultraviolet warning technology has high environmental adaptability, the low false alarm rate, small volume and other advantages, in the military field applications it has been developed rapidly. For the ultraviolet warning system, the optimal working waveband is 250 nm 280 nm (Solar Blind UV) due to the strong absorption of ozone layer. According to current application demands for solar blind ultraviolet detection and warning, this paper proposes ultraviolet warning optical system based on interference imaging, which covers solar blind ultraviolet (250nm-280nm) and dual field. This structure includes a primary optical system, an ultraviolet reflector array, an ultraviolet imaging system and an ultraviolet interference imaging system. It makes use of an ultraviolet beam-splitter to achieve the separation of two optical systems. According to the detector and the corresponding application needs of two visual field of the optical system, the calculation and optical system design were completed. After the design, the MTF of the two optical system is more than 0.8@39lp/mm.A single pixel energy concentration is greater than 80%.

Combined effects of lanthanum(III) and elevated ultraviolet-B radiation on root growth and ion absorption in soybean seedlings.

PubMed

Huang, Guang Rong; Wang, Li Hong; Zhou, Qing

2014-03-01

Rare earth element accumulation in the soil and elevated ultraviolet (UV)-B radiation (280-315 nm) are important environmental issues worldwide. To date, there have been no reports concerning the combined effects of lanthanum (La)(III) and elevated UV-B radiation on plant roots in regions where the two issues occur simultaneously. Here, the combined effects of La(III) and elevated UV-B radiation on the growth, biomass, ion absorption, activities, and membrane permeability of roots in soybean (Glycine max L.) seedlings were investigated. A 0.08 mmol L(-1) La(III) treatment improved the root growth and biomass of soybean seedlings, while ion absorption, activities, and membrane permeability were obviously unchanged; a combined treatment with 0.08 mmol L(-1) La(III) and elevated UV-B radiation (2.63/6.17 kJ m(-2) day(-1)) exerted deleterious effects on the investigated indices. The deleterious effects were aggravated in the other combined treatments and were stronger than those of treatments with La(III) or elevated UV-B radiation alone. The combined treatment with 0.24/1.20 mmol L(-1) La(III) and elevated UV-B radiation exerted synergistically deleterious effects on the growth, biomass, ion absorption, activities, and membrane permeability of roots in soybean seedlings. In addition, the deleterious effects of the combined treatment on the root growth were due to the inhibition of ion absorption induced by the changes in the root activity and membrane permeability.

Ultraviolet photography of the in vivo human cornea unmasks the Hudson-Stähli line and physiologic vortex patterns.

PubMed

Every, Sean G; Leader, John P; Molteno, Anthony C B; Bevin, Tui H; Sanderson, Gordon

2005-10-01

To perform ultraviolet (UV) macrophotography of the normal in vivo human cornea, establishing biometric data of the major component of UV absorption for comparison with the Hudson-Stähli (HS) line, the distribution of iron demonstrated by Perl stain, and cases of typical amiodarone keratopathy. Nonrandomized comparative case series of UV photographs of 76 normal corneas (group 1) and 16 corneas with typical amiodarone keratopathy (group 2). Image-analysis software was used to grade the major component of UV absorption for slope and the coordinates of its points of intersection with the vertical corneal meridian and inflection. In group 1 the major component had a mean slope of 5.8 degrees, sloping down from nasal to temporal cornea. The mean coordinates of points of intersection with the vertical corneal meridian and inflection were (0, 0.30) and (0.02, 0.31), respectively. No significant differences between groups 1 and 2 were found for slope (P = 0.155), intersection with the vertical corneal meridian (P = 0.517), and point of inflection (P = 0.344). The major component of UV absorption was consistent with published characteristics of the HS line, and coincidence of UV absorption and Perl-stained iron was demonstrated in one corneal button. A vortex pattern of UV absorption was observed in all corneas. UV photography demonstrates subclinical corneal iron, confirming its deposition in an integrated HS line/vortex pattern. Coincident iron and amiodarone deposition occurs in amiodarone keratopathy.

Geometrical-optics code for computing the optical properties of large dielectric spheres.

PubMed

Zhou, Xiaobing; Li, Shusun; Stamnes, Knut

2003-07-20

Absorption of electromagnetic radiation by absorptive dielectric spheres such as snow grains in the near-infrared part of the solar spectrum cannot be neglected when radiative properties of snow are computed. Thus a new, to our knowledge, geometrical-optics code is developed to compute scattering and absorption cross sections of large dielectric particles of arbitrary complex refractive index. The number of internal reflections and transmissions are truncated on the basis of the ratio of the irradiance incident at the nth interface to the irradiance incident at the first interface for a specific optical ray. Thus the truncation number is a function of the angle of incidence. Phase functions for both near- and far-field absorption and scattering of electromagnetic radiation are calculated directly at any desired scattering angle by using a hybrid algorithm based on the bisection and Newton-Raphson methods. With these methods a large sphere's absorption and scattering properties of light can be calculated for any wavelength from the ultraviolet to the microwave regions. Assuming that large snow meltclusters (1-cm order), observed ubiquitously in the snow cover during summer, can be characterized as spheres, one may compute absorption and scattering efficiencies and the scattering phase function on the basis of this geometrical-optics method. A geometrical-optics method for sphere (GOMsphere) code is developed and tested against Wiscombe's Mie scattering code (MIE0) and a Monte Carlo code for a range of size parameters. GOMsphere can be combined with MIE0 to calculate the single-scattering properties of dielectric spheres of any size.

Brown and black carbon in Beijing aerosol: Implications for the effects of brown coating on light absorption by black carbon.

PubMed

Cheng, Yuan; He, Ke-Bin; Engling, Guenter; Weber, Rodney; Liu, Jiu-Meng; Du, Zhen-Yu; Dong, Shu-Ping

2017-12-01

Brown carbon (BrC) is increasingly included in climate models as an emerging category of particulate organic compounds that can absorb solar radiation efficiently at specific wavelengths. Water-soluble organic carbon (WSOC) has been commonly used as a surrogate for BrC; however, it only represents a limited fraction of total organic carbon (OC) mass, which could be as low as about 20% in urban atmosphere. Using methanol as the extraction solvent, up to approximately 90% of the OC in Beijing aerosol was isolated and measured for absorption spectra over the ultraviolet-to-visible wavelength range. Compared to methanol-soluble OC (MSOC), WSOC underestimated BrC absorption by about 50% at 365nm. The mass absorption efficiencies measured for BrC in Beijing aerosol were converted to the imaginary refractive indices of BrC and subsequently used to compute BrC coating-induced enhancement of light absorption (E abs ) by black carbon. E abs attributed to lensing was reduced in the case of BrC coating relative to that caused by purely-scattering coating. However, this reduction was overwhelmed by the effect of BrC shell absorption, indicating that the overall effect of BrC coating was an increase in E abs . Methanol extraction significantly reduced charring of OC during thermal-optical analysis, leading to a large increase in the measured elemental carbon (EC) mass and an apparent improvement in the consistency of EC measurements by different thermal-optical methods. Copyright © 2017 Elsevier B.V. All rights reserved.

Ultraviolet-Absorption Spectroscopic Biofilm Monitor

NASA Technical Reports Server (NTRS)

Micheels, Ronald H.

2004-01-01

An ultraviolet-absorption spectrometer system has been developed as a prototype instrument to be used in continuous, real-time monitoring to detect the growth of biofilms. Such monitoring is desirable because biofilms are often harmful. For example, biofilms in potable-water and hydroponic systems act as both sources of pathogenic bacteria that resist biocides and as a mechanism for deterioration (including corrosion) of pipes. Biofilms formed from several types of hazardous bacteria can thrive in both plant-growth solutions and low-nutrient media like distilled water. Biofilms can also form in condensate tanks in air-conditioning systems and in industrial heat exchangers. At present, bacteria in potable-water and plant-growth systems aboard the space shuttle (and previously on the Mir space station) are monitored by culture-plate counting, which entails an incubation period of 24 to 48 hours for each sample. At present, there are no commercially available instruments for continuous monitoring of biofilms in terrestrial or spaceborne settings.

Compact high-pulse-energy ultraviolet laser source for ozone lidar measurements.

PubMed

Elsayed, Khaled A; DeYoung, Russell J; Petway, Larry B; Edwards, William C; Barnes, James C; Elsayed-Ali, Hani E

2003-11-20

An all solid-state Ti:sapphire laser differential absorption lidar transmitter was developed. This all-solid-state laser provides a compact, robust, and highly reliable laser transmitter for potential application in differential absorption lidar measurements of atmospheric ozone. Two compact, high-energy-pulsed, and injection-seeded Ti:sapphire lasers operating at a pulse repetition frequency of 30 Hz and wavelengths of 867 and 900 nm, with M2 of 1.3, have been experimentally demonstrated and their properties compared with model results. The output pulse energy was 115 mJ at 867 nm and 105 mJ at 900 nm, with a slope efficiency of 40% and 32%, respectively. At these energies, the beam quality was good enough so that we were able to achieve 30 mJ of ultraviolet laser output at 289 and 300 nm after frequency tripling with two lithium triborate nonlinear crystals.

Measurement of free radical kinetics in pulsed plasmas by UV and VUV absorption spectroscopy and by modulated beam mass spectrometry

NASA Astrophysics Data System (ADS)

Cunge, G.; Bodart, P.; Brihoum, M.; Boulard, F.; Chevolleau, T.; Sadeghi, N.

2012-04-01

This paper reviews recent progress in the development of time-resolved diagnostics to probe high-density pulsed plasma sources. We focus on time-resolved measurements of radicals' densities in the afterglow of pulsed discharges to provide useful information on production and loss mechanisms of free radicals. We show that broad-band absorption spectroscopy in the ultraviolet and vacuum ultraviolet spectral domain and threshold ionization modulated beam mass spectrometry are powerful techniques for the determination of the time variation of the radicals' densities in pulsed plasmas. The combination of these complementary techniques allows detection of most of the reactive species present in industrial etching plasmas, giving insights into the physico-chemistry reactions involving these species. As an example, we discuss briefly the radicals' kinetics in the afterglow of a SiCl4/Cl2/Ar discharge.

Protective effect of maghemite nanoparticles on ultraviolet-induced photo-damage in human skin fibroblasts

NASA Astrophysics Data System (ADS)

Lee, Kwon-Jai; An, Jeung-Hee; Shin, Jae-Soo; Kim, Dong-Hee; Kim, Changman; Ozaki, Hajime; Koh, Jae-Gui

2007-11-01

This study examined the optical properties of an oxidized form of maghemite (γ-Fe2O3) nanoparticles and their protective effects against the photoaging of human skin fibroblasts irradiated with ultraviolet (UV) light. Nanoparticles with diameters ranging from 8.7 to 12 nm were prepared using a chemical co-precipitation method. The nanoparticles were coated with two surfactants to obtain a water-based product. The onset of the absorption of the γ-Fe2O3 nanoparticles in the UV-visible absorption spectra increased with increasing particle size. The γ-Fe2O3 nanoparticles significantly inhibited the production of matrix metalloproteinase-1 in human skin fibroblast HS 68 cells by 60% compared with the UV-irradiated control. These results suggest that γ-Fe2O3 nanoparticles have photoprotective properties, and have potential use as an agent against photoaging.

Composition and thermal profiles of the Jovian upper atmosphere determined by the Voyager ultraviolet stellar occultation experiment

NASA Technical Reports Server (NTRS)

Festou, M. C.; Atreya, S. K.; Donahue, T. M.; Sandel, B. R.; Shemansky, D. E.; Broadfoot, A. L.

1981-01-01

During the occultation of the star Regulus (B7 type) by Jupiter as seen from the Voyager 2 spacecraft on July 9, 1979, two absorbing regions were detected. Between 911 and 1200 A, H2 was absorbing over a 600 km altitude range. Above 1300 A, the rapid increase of the absorption by the hydrocarbons was observed over an altitude interval of approximately 100 km with a height resolution of 3 km. The analysis of these absorption features has provided the height profiles of molecular hydrogen, methane, ethane, and acetylene, as well as the thermal profile in the upper atmosphere of Jupiter. Combining the Voyager ultraviolet spectrometer results with other data, such as those obtained by the Voyager infrared and radioscience instruments, has yielded a comprehensive model of the composition and structure of the atmosphere of Jupiter.

Assessment of Transition Element Speciation in Glasses Using a Portable Transmission Ultraviolet-Visible-Near-Infrared (UV-Vis-NIR) Spectrometer.

PubMed

Hunault, Myrtille; Lelong, Gérald; Gauthier, Michel; Gélébart, Frédéric; Ismael, Saindou; Galoisy, Laurence; Bauchau, Fanny; Loisel, Claudine; Calas, Georges

2016-05-01

A new low-cost experimental setup based on two compact dispersive optical spectrometers has been developed to measure optical absorption transmission spectra over the 350-2500 nm energy range. We demonstrate how near-infrared (NIR) data are essential to identify the coloring species in addition to ultraviolet visible data. After calibration with reference glasses, the use of an original sample stage that maintains the window panel in the vertical position enables the comparison of ancient and modern glasses embedded in a panel from the Sainte-Chapelle of Paris, without any sampling. The spectral resolution enables to observe fine resonances arising in the absorption bands of Cr(3+), and the complementary information obtained in the NIR enables to determine the contribution of Fe(2+), a key indicator of glassmaking conditions. © The Author(s) 2016.

Hard X-ray tests of the unified model for an ultraviolet-detected sample of Seyfert 2 galaxies

NASA Technical Reports Server (NTRS)

Mulchaey, John S.; Myshotzky, Richard F.; Weaver, Kimberly A.

1992-01-01

An ultraviolet-detected sample of Seyfert 2 galaxies shows heavy photoelectric absorption in the hard X-ray band. The presence of UV emission combined with hard X-ray absorption argues strongly for a special geometry which must have the general properties of the Antonucci and Miller unified model. The observations of this sample are consistent with the picture in which the hard X-ray photons are viewed directly through the obscuring matter (molecular torus?) and the optical, UV, and soft X-ray continuum are seen in scattered light. The large range in X-ray column densities implies that there must be a large variation in intrinsic thicknesses of molecular tori, an assumption not found in the simplest of unified models. Furthermore, constraints based on the cosmic X-ray background suggest that some of the underlying assumptions of the unified model are wrong.

The outer atmospheres of cool M giants: High-dispersion ultraviolet spectra of Rho Per, 2 Cen, and g Her

NASA Technical Reports Server (NTRS)

Eaton, Joel A.; Johnson, Hollis R.

1986-01-01

Long duration IUE spectra were obtained to extend coverage of cool giants studied in the ultraviolet at high dispersion to M6. The chromospheric spectra of the three stars, which consist of a profusion of Fe II lines and a few lines of Mg II, Mg I, Al II, C II, C I, Cr II, and Fe I, are remarkably similar, both among themselves and with respect to stars of earlier spectral type. These lines present a picture of a warm chromosphere that is static in the average but may be far from uniform in density and ionization. The Mg II emission lines of 2 Cen show 2 unresolved absorption components, the shorter at the velocity of the local interstellar medium. The longer is blueshifted from the star by 12 to 18 km/sec and must be one of very few observed shell lines uncontaminated by interstellar absorption.

Theoretical and experimental studies of the Nd3+ 4f3<-->4f25d transitions in monoclinic Nd:BaY2F8 crystal

NASA Astrophysics Data System (ADS)

Collombet, Annabelle; Guyot, Yannick; Joubert, Marie-France; Margerie, Jean; Moncorgé, Richard; Tkachuk, Alexandra

2004-11-01

Experimental spectroscopic results related to Nd3+-doped BaY2F8, are presented that include vacuum-ultraviolet ground-state absorption and excitation spectra as well as polarized emission and excited-state absorption spectra recorded in the near-ultraviolet spectral range at room and low temperatures. Calculations were performed to determine the positions of the 4f25d sublevels and the intensities and polarizations of the 4f3<-->4f25d optical transitions of the Nd3+ ions in the C2 symmetry sites of the biaxial host crystal. The simulated spectra agree well with the experimental spectra; in particular, the model that was used successfully reproduced the differences between the polarized spectra on one hand and between the spectra recorded at low and room temperatures on the other hand.

Multilayer thin film design for far ultraviolet polarizers using an induced transmission and absorption technique

NASA Technical Reports Server (NTRS)

Kim, Jongmin; Zukic, Muamer; Torr, Douglas G.

1993-01-01

An explanation of induced transmission for spectral regions excluding the far ultraviolet (FUV) is given to better understand how induced transmission and absorption can be used to design effective polarizers in the FUV spectral region. We achieve high s-polarization reflectance and a high degree of polarization (P equals (Rs-Rp)/(Rs+Rp)) by means of a MgF2/Al/MgF2 three layer structure on an opaque thick film of Al as the substrate. For example, our polarizer designed for the Lyman-alpha line (lambda equals 121.6 nm) has 87.95 percent reflectance for the s-polarization case and 0.43 percent for the p-polarization case, with a degree of polarization of 99.03 percent. If a double reflection polarizer is made with this design, it will have a degree of polarization of 99.99 percent and s-polarization throughput of 77.35 percent.

Lifetimes and f-values of the D 2Σ- ← X 2Π system of OH and OD

NASA Astrophysics Data System (ADS)

Heays, Alan; de Oliveira, Nelson; Gans, Bérenger; Ito, Kenji; Boyé-Péronne, Séverine; Douin, Stéphane; Hickson, Kevin; Nahon, Laurent; Loison, Jean-Christophe

2017-10-01

The OH radical is abundant in the interstellar medium and cometary comae, where it plays a significant role in the photochemical cycle of water. Also, the oxidising potential of the Earth atmosphere is influenced by this molecule. The OH lifetime in the presence of ultraviolet radiation is of prime interest in all these locations. The vacuum-ultraviolet absorption of the D 2Σ- ← X 2Π system contributes to a reduction of this lifetime. It also provides an independent way to observe the OH molecule in the interstellar medium. But a reliable oscillator strength (f-value) is needed. Vacuum-ultraviolet absorption of the D 2Σ- ← X 2Π system of OH and OD was recorded with high spectral resolution in a plasma-discharge radical source and using synchrotron radiation coupled to the unique ultraviolet Fourier-transform spectrometer on the DESIRS beamline of synchrotron SOLEIL. Line oscillator strengths are absolutely calibrated with respect to the well-known A 2Σ+ ← X 2Π system. The new oscillator strength decreases the best-estimate lifetime of OH in an interstellar radiation field and reduces its uncertainty. We also measured line broadening of the excited D 2Σ- v=0 and 1 levels for the first time and find a lifetime for these states which is 5 times shorter than theoretically predicted.This new data will aid in the interpretation of astronomical observations and help improve photochemical models in many contexts.

The missing UV absorption lines of NGC 4151

NASA Technical Reports Server (NTRS)

Leech, K. J.; Penston, M. V.; Snijders, M. A. J.; Ward, M. J.; Gull, T. R.

1990-01-01

Near simultaneous high dispersion long and short wavelength International Ultraviolet Explorer (IUE) observations of the Seyfert galaxy NGC 4151 are discussed. Previous observations revealed a narrow absorption system in Mg II not present in Ly alpha or C IV. The new observations confirm the presence of this system in Mg II and its absence in the other lines. Possible reasons for this are discussed. Future Hubble Space Telescope studies of NGC 4151 are discussed.

Photo-oxidation of polymer-like amorphous hydrogenated carbon under visible light illumination

DOE PAGES

Baxamusa, Salmaan; Laurence, Ted; Worthington, Matthew; ...

2015-11-10

Amorphous hydrogenated carbon (a-C:H), a polymer-like network typically synthesized by plasma chemical vapor deposition, has long been understood to exhibit optical absorption of visible light (λ > 400 nm). In this report we explain that this absorption is accompanied by rapid photo-oxidation (within minutes) that behaves in most respects like classic polymer photo-oxidation with the exception that it occurs under visible light illumination rather than ultraviolet illumination.

Absorption Cross-Sections of Sodium Diatomic Molecules

NASA Technical Reports Server (NTRS)

Fong, Zeng-Shevan

1985-01-01

The absorption cross sections of sodium dimers were studied using a heat pipe over operating in the non-heat-pipe mode. Three wavelength regions were observed. They are in the red, the green-blue, and the near ultraviolet regions. The absorption cross section depends on the wavelength of the incident light. Representative peak values for the v"=0 progression in the red and green-blue regions are 2.59 A sup 2 (average value) and 11.77 A sup 2 (T sub ave=624 K). The value for the C greater than X transitions is several tenths A sup 2. The cross sections were measured from absorption spectra taken as a function of temperature.

Probing ultrafast spin dynamics with high-harmonic magnetic circular dichroism spectroscopy

NASA Astrophysics Data System (ADS)

Willems, F.; Smeenk, C. T. L.; Zhavoronkov, N.; Kornilov, O.; Radu, I.; Schmidbauer, M.; Hanke, M.; von Korff Schmising, C.; Vrakking, M. J. J.; Eisebitt, S.

2015-12-01

Magnetic circular dichroism in the extreme ultraviolet (XUV) spectral range is a powerful technique for element-specific probing of magnetization in multicomponent magnetic alloys and multilayers. We combine a high-harmonic generation source with a λ /4 phase shifter to obtain circularly polarized XUV femtosecond pulses for ultrafast magnetization studies. We report on simultaneously measured resonant magnetic circular dichroism (MCD) of Co and Ni at their respective M2 ,3 edges and of Pt at its O edge, originating from interface magnetism. We present a time-resolved MCD absorption measurement of a thin magnetic Pt/Co/Pt film, showing simultaneous demagnetization of Co and Pt on a femtosecond time scale.

Influence of environmental factors on spectral characteristic of chromophoric dissolved organic matter (CDOM) in Inner Mongolia Plateau, China

NASA Astrophysics Data System (ADS)

Wen, Z. D.; Song, K. S.; Zhao, Y.; Du, J.; Ma, J. H.

2015-06-01

Spectral characteristics of chromophoric dissolved organic matter (CDOM) were examined in conjunction with environmental factors in the waters of 22 rivers and 26 terminal waters in Hulun Buir plateau, northeast China. Dissolved organic carbon (DOC), total nitrogen (TN), and total phosphorous (TP) were significantly higher in terminal waters than rivers waters (p < 0.01). Principal component analysis (PCA) indicated that non-water light absorption and anthropogenic nutrient disturbances might be the causes of the diversity of water quality parameters in Hulun Buir plateau. CDOM absorption in river waters was significantly lower than terminal waters (p < 0.01). Analysis of ratio of absorption at 250-365 nm (E250 : 365), specific UV absorbance (SUVA254), and spectral slope ratio (Sr) indicated that CDOM in river waters had higher aromaticity, molecular weight, and vascular plant contribution than in terminal waters. Furthermore, results showed that DOC concentration, CDOM light absorption, and the proportion of autochthonous sources of CDOM in plateau waters were all higher than in other freshwater rivers reported in the literature. The strong evapoconcentration, intense ultraviolet irradiance and landscape features of Hulun Buir plateau may be responsible for the above phenomenon. Redundancy analysis (RDA) indicated that the environmental variables TSM, TN, and EC had a strong correlation with light absorption characteristics, followed by TDS and chlorophyll a. In most sampling locations, CDOM was the dominant non-water light-absorbing substance. Light absorption by non-algal particles often exceeded that by phytoplankton in the plateau waters. Study of these optical-physicochemical correlations is helpful in the evaluation of the potential influence of water quality factors on non-water light absorption in cold plateau water environments. And the study on organic carbon in plateau lakes had a vital contribution to global carbon balance estimation.

Multi-wavelength Characterization of Brown and Black Carbon from Filter Samples

NASA Astrophysics Data System (ADS)

Johnson, M. M.; Yatavelli, R. L. N.; Chen, L. W. A. A.; Gyawali, M. S.; Arnott, W. P.; Wang, X.; Chakrabarty, R. K.; Moosmüller, H.; Watson, J. G.; Chow, J. C.

2014-12-01

Particulate matter (PM) scatters and absorbs solar radiation and thereby affects visibility, the Earth's radiation balance, and properties and lifetimes of clouds. Understanding the radiative forcing (RF) of PM is essential to reducing the uncertainty in total anthropogenic and natural RF. Many instruments that measure light absorption coefficients (βabs [λ], Mm-1) of PM have used light at near-infrared (NIR; e.g., 880 nm) or red (e.g., 633 nm) wavelengths. Measuring βabs over a wider wavelength range, especially including the ultraviolet (UV) and visible, allows for contributions from black carbon (BC), brown carbon (BrC), and mineral dust (MD) to be differentiated. This will help to determine PM RF and its emission sources. In this study, source and ambient samples collected on Teflon-membrane and quartz-fiber filters are used to characterize and develop a multi-wavelength (250 - 1000 nm) filter-based measurement method of PM light absorption. A commercially available UV-visible spectrometer coupled with an integrating sphere is used for quantifying diffuse reflectance and transmittance of filter samples, from which βabs and absorption Ǻngström exponents (AAE) of the PM deposits are determined. The filter-based light absorption measurements of laboratory generated soot and biomass burning aerosol are compared to 3-wavelength photoacoustic absorption measurements to evaluate filter media and loading effects. Calibration factors are developed to account for differences between filter types (Teflon-membrane vs. quartz-fiber), and between filters and in situ photoacoustic absorption values. Application of multi-spectral absorption measurements to existing archived filters, including specific source samples (e.g. diesel and gasoline engines, biomass burning, dust), will also be discussed.

Combined infrared and ultraviolet-visible spectroscopy matrix-isolated carbon vapor

NASA Technical Reports Server (NTRS)

Kurtz, Joe; Huffman, Donald R.

1990-01-01

Infrared and UV-visible absorption spectra have been measured on the same sample of matrix-isolated carbon vapor in order to establish correlations between absorption intensities of vibrational and electronic transitions as a function of sample annealing. A high degree of correlation has been found between the IR feature at 1998/cm recently assigned to C8 and a UV absorption feature at about 3100 A. Thus, for the first time, direct evidence is given for the assignment of one of the unknown UV-visible features of the long-studied matrix-isolated carbon vapor spectrum.

A new model for Mars atmospheric dust based upon analysis of ultraviolet through infrared observations from Mariner 9, Viking, and Phobos

NASA Technical Reports Server (NTRS)

Clancy, R. T.; Lee, S. W.; Gladstone, G. R.; McMillan, W. W.; Rousch, T.

1995-01-01

We propose key modifications to the Toon et al. (1977) model of the particle size distribution and composition of Mars atmospheric dust, based on a variety of spacecraft and wavelength observations of the dust. A much broader (r(sub eff)variance-0.8 micron), smaller particle size (r(sub mode)-0.02 microns) distribution coupled with a "palagonite-like" composition is argued to fit the complete ultraviolet-to-30-micron absorption properties of the dust better than the montmorillonite-basalt r(sub eff)variance= 0.4 micron, r(sub mode)= 0.40 micron dust model of Toon et al. Mariner 9 (infrared interferometer spectrometer) IRIS spectra of high atmospheric dust opacities during the 1971 - 1972 Mars global dust storm are analyzed in terms of the Toon et al. dust model, and a Hawaiian palagonite sample with two different size distribution models incorporating smaller dust particle sizes. Viking Infrared Thermal Mapper (IRTM) emission-phase-function (EPF) observations at 9 microns are analyzed to retrieve 9-micron dust opacities coincident with solar band dust opacities obtained from the same EPF sequences. These EPF dust opacities provide an independent measurement of the visible/9-microns extinction opacity ratio (> or equal to 2) for Mars atmospheric dust, which is consistent with a previous measurement by Martin (1986). Model values for the visible/9-microns opacity ratio and the ultraviolet and visible single-scattering albedos are calculated for the palagonite model with the smaller particle size distributions and compared to the same properties for the Toon et al. model of dust. The montmorillonite model of the dust is found to fit the detailed shape of the dust 9-micron absorption well. However, it predicts structured, deep absorptions at 20 microns which are not observed and requires a separate ultraviolet-visible absorbing component to match the observed behavior of the dust in this wavelength region. The modeled palagonite does not match the 8- to 9-micron absorption presented by the dust in the IRIS spectra, probably due to its low SiO2 content (31%). However, it does provide consistent levels of ultraviolet/visible absorption, 9- to 12-micron absorption, and a lack of structured absorption at 20 microns. The ratios of dust extinction opacities at visible, 9 microns, and 30 microns are strongly affected by the dust particle size distribution. The Toon et al. dust size distribution (r(sub mode)= 0.40, r(sub eff)variance= 0.4 microns, r(sub cw mu)= 2.7 microns) predicts the correct ratio of the 9- to 30-micron opacity, but underpredicts the visible/9-micron opacity ratio considerably (1 versus > or equal to 2). A similar particle distribution width with smaller particle sizes (r(sub mode)= 0.17, r(sub eff)variance= 0.4 microns, r(sub cw mu)=1.2 microns) will fit the observed visible/9-micron opacity ratio, but overpredicts the observed 9-micron/30-micron opacity ratio. A smaller and much broader particle size distribution (r(sub mode)= 0.02, r(sub eff)variance= 0.8 microns, r(sub cw mu)= 1.8 microns) can fit both dust opacity ratios. Overall, the nanocrystalline structure of palagonite coupled with a smaller, broader distribution of dust particle sizes provides a more consistent fit than the Toon et al. model of the dust to the IRIS spectra, the observed visible/9-micron dust opacity ratio, the Phobos occultation measurements of dust particle sizes, and the weakness of surface near IR absorptions expected for clay minerals.

Bandgap-Engineered Zinc-Tin-Oxide Thin Films for Ultraviolet Sensors.

PubMed

Cheng, Tien-Hung; Chang, Sheng-Po; Chang, Shoou-Jinn

2018-07-01

Zinc-tin-oxide thin-film transistors were prepared by radio frequency magnetron co-sputtering, while an identical zinc-tin-oxide thin film was deposited simultaneously on a clear glass substrate to facilitate measurements of the optical properties. When we adjusted the deposition power of ZnO and SnO2, the bandgap of the amorphous thin film was dominated by the deposition power of SnO2. Since the thin-film transistor has obvious absorption in the ultraviolet region owing to the wide bandgap, the drain current increases with the generation of electron-hole pairs. As part of these investigations, a zinc-tin-oxide thin-film transistor has been fabricated that appears to be very promising for ultraviolet applications.

Transition state region in the A-Band photodissociation of allyl iodide—A femtosecond extreme ultraviolet transient absorption study

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bhattacherjee, Aditi, E-mail: abhattacherjee@berkeley.edu, E-mail: andrewattar@berkeley.edu; Attar, Andrew R., E-mail: abhattacherjee@berkeley.edu, E-mail: andrewattar@berkeley.edu; Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720

2016-03-28

Femtosecond extreme ultraviolet (XUV) transient absorption spectroscopy based on a high-harmonic generation source is used to study the 266 nm induced A-band photodissociation dynamics of allyl iodide (CH{sub 2} =CHCH{sub 2}I). The photolysis of the C—I bond at this wavelength produces iodine atoms both in the ground ({sup 2}P{sub 3/2}, I) and spin-orbit excited ({sup 2}P{sub 1/2}, I*) states, with the latter as the predominant channel. Using XUV absorption at the iodine N{sub 4/5} edge (45–60 eV), the experiments constitute a direct probe of not only the long-lived atomic iodine reaction products but also the fleeting transition state region ofmore » the repulsive n{sub I}σ{sup ∗}{sub C—I} excited states. Specifically, three distinct features are identified in the XUV transient absorption spectrum at 45.3 eV, 47.4 eV, and 48.4 eV (denoted transients A, B, and C, respectively), which arise from the repulsive valence-excited nσ{sup ∗} states and project onto the high-lying core-excited states of the dissociating molecule via excitation of 4d(I) core electrons. Transients A and B originate from 4d(I) → n(I) core-to-valence transitions, whereas transient C is best assigned to a 4d(I) →σ{sup ∗}(C—I) transition. The measured differential absorbance of these new features along with the I/I* branching ratios known from the literature is used to suggest a more definitive assignment, albeit provisional, of the transients to specific dissociative states within the A-band manifold. The transients are found to peak around 55 fs–65 fs and decay completely by 145 fs–185 fs, demonstrating the ability of XUV spectroscopy to map the evolution of reactants into products in real time. The similarity in the energies of transients A and B with analogous features observed in methyl iodide [Attar et al. J. Phys. Chem. Lett. 6, 5072, (2015)] together with the new observation of transient C in the present work provides a more complete picture of the valence electronic structure in the transition state region. The results provide a benchmark for theoretical calculations on the nature of core-excited states in halogenated hydrocarbons, especially in the transition state region along the C—I reaction coordinate.« less

40 CFR 796.1050 - Absorption in aqueous solution: Ultraviolet/visible spectra.

Code of Federal Regulations, 2010 CFR

2010-07-01

... organic solvent should be used (methanol preferred). (3) The acid medium should have a pH of less than 2...) Milazzo, G., Caroli, S., Palumbo-Doretti, M., Violante, N., Analytical Chemistry, 49: 711 (1977). (2...

[Purification and structural identification of herbicides from Botrytis cinerea].

PubMed

Zheng, Meng; Xu, Kuo; Dong, Jingao

2008-10-01

Toxin produced by phytopathogenic fungi is one of the important microbial herbicides. We found a new compound with herbicidal activity. Five different ultraviolet absorption components were isolated from the filtrate of Botrytis cinerea isolate 7-3 culture. Of the five components, one showed strong inhibitory to Digitaria sanguinalis. The pure fraction with high herbicidal activity was obtained by HPLC purification. Its structure was identified as 10-syn-dihydrobotrydial by Ultraviolet and Visible Spectroscopy, Infrared Spectrum, Nuclear Magnetic Resonance Spectroscopy analysis. The findings are important for future preparation and application of the herbicide.

Androgenic alopecia may have evolved to protect men from prostate cancer by increasing skin exposure to ultraviolet radiation.

PubMed

Kabai, Peter

2008-01-01

Androgenic alopecia affects populations adapted to colder climate, and individuals at an age and hormonal status susceptible to prostate cancer. Male pattern baldness enhances absorption of UV radiation on the top of the head, an area directly exposed to sunlight during everyday activities. Ultraviolet radiation is reported to reduce the risk of advanced prostate cancer. Here I propose that progression of androgenic alopecia rather than being a risk factor is a finely tuned mechanism evolved to protect against prostate cancer.

Photoluminescence emission spectra of Makrofol® DE 1-1 upon irradiation with ultraviolet radiation

NASA Astrophysics Data System (ADS)

El Ghazaly, M.; Aydarous, Abdulkadir

Photoluminescence (PL) emission spectra of Makrofol® DE 1-1 (bisphenol-A based polycarbonate) upon irradiation with ultraviolet radiation of different wavelengths were investigated. The absorption-and attenuation coefficient measurements revealed that the Makrofol® DE 1-1 is characterized by high absorbance in the energy range 6.53-4.43 eV but for a lower energy than 4.43 eV, it is approximately transparent. Makrofol® DE 1-1 samples were irradiated with ultraviolet radiation of wavelength in the range from 250 (4.28 eV) to 400 (3.10 eV) nm in step of 10 nm and the corresponding photoluminescence (PL) emission spectra were measured with a spectrofluorometer. It is found that the integrated counts and the peak height of the photoluminescence emission (PL) bands are strongly correlated with the ultraviolet radiation wavelength. They are increased at the ultraviolet radiation wavelength 280 nm and have maximum at 290 nm, thereafter they decrease and diminish at 360 nm of ultraviolet wavelength. The position of the PL emission band peak was red shifted starting from 300 nm, which increased with the increase the ultraviolet radiation wavelength. The PL bandwidth increases linearly with the increase of the ultraviolet radiation wavelength. When Makrofol® DE 1-1 is irradiated with ultraviolet radiation of short wavelength (UVC), the photoluminescence emission spectra peaks also occur in the UVC but of a relatively longer wavelength. The current new findings should be considered carefully when using Makrofol® DE 1-1 in medical applications related to ultraviolet radiation.

Protection of Nomex from Ultraviolet Degradation

DTIC Science & Technology

1977-03-01

absorbs UV radiation beginning at approximately 390 nano- meters (nm) and extending into the near UV with a peak at approximately 360 nm. This absorption is...the region near 290 nm [ 5 ]. Sunlight is much richer in radiation at 360 nm than at 290 nm and this fact undoubt- edly accounts for the much greater...function as UV screening agents. The absorption spectrum of Nomex in the near UV and visible region which is responsible for Nomex photodegra- dation is

VUV spectroscopic study of the ? state of H2

NASA Astrophysics Data System (ADS)

Dickenson, G. D.; Ubachs, W.

2014-04-01

Spectral lines, probing rotational quantum states J‧ = 0, 1, 2 of the inner well vibrations (υ‧ ≤ 8) in the ? state of molecular hydrogen, were recorded in high resolution using a vacuum ultraviolet Fourier transform absorption spectrometer in the wavelength range 73-86 nm. Accurate line positions and predissociation widths are determined from a fit to the absorption spectra. Improved values for the line positions are obtained, while the predissociation widths agree well with previous investigations.

Polymeric Luminescent Compositions Doped with Beta-Diketonates Boron Difluoride as Material for Luminescent Solar Concentrator

NASA Astrophysics Data System (ADS)

Khrebtov, A. A.; Fedorenko, E. V.; Reutov, V. A.

2017-11-01

In this paper we investigated polymeric luminescent compositions based on polystyrene doped with beta diketonates boron difluoride. Transparent films with effective absorption in the ultraviolet and blue regions of the spectrum were obtained. Polymeric luminescent compositions based on the mixture of dyes allow expanding the absorption region and increase the radiation shift. A luminescent solar concentrator consisting of a glass plate coated with such film can be used for photovoltaic window application.

When galaxies collide: understanding the broad absorption-line radio galaxy 4C +72.26

NASA Astrophysics Data System (ADS)

Smith, D. J. B.; Simpson, C.; Swinbank, A. M.; Rawlings, S.; Jarvis, M. J.

2010-05-01

We present a range of new observations of the `broad absorption-line radio galaxy' 4C +72.26 (z ~ 3.5), including sensitive rest-frame ultraviolet integral field spectroscopy using the Gemini/GMOS-N instrument and Subaru/CISCO K-band imaging and spectroscopy. We show that 4C +72.26 is a system of two vigorously star-forming galaxies superimposed along the line of sight separated by ~1300 +/- 200 km s-1 in velocity, with each demonstrating spectroscopically resolved absorption lines. The most active star-forming galaxy also hosts the accreting supermassive black hole which powers the extended radio source. We conclude that the star formation is unlikely to have been induced by a shock caused by the passage of the radio jet, and instead propose that a collision is a more probable trigger for the star formation. Despite the massive starburst, the ultraviolet-mid-infrared spectral energy distribution suggests that the pre-existing stellar population comprises ~1012Msolar of stellar mass, with the current burst only contributing a further ~2 per cent, suggesting that 4C +72.26 has already assembled most of its final stellar mass.

The Surprising Absence of Absorption in the Far-ultraviolet Spectrum of Mrk 231

NASA Technical Reports Server (NTRS)

Veilleux, S.; Trippe, M.; Hamann, F.; Rupke, D. S. N.; Tripp, T. M.; Netzer, H.; Lutz, D.; Sembach, K. R.; Krug, H.; Teng, Stacy H.;

Ultrafast carrier thermalization and trapping in silicon-germanium alloy probed by extreme ultraviolet transient absorption spectroscopy

PubMed Central

Zürch, Michael; Chang, Hung-Tzu; Kraus, Peter M.; Cushing, Scott K.; Borja, Lauren J.; Gandman, Andrey; Kaplan, Christopher J.; Oh, Myoung Hwan; Prell, James S.; Prendergast, David; Pemmaraju, Chaitanya D.; Neumark, Daniel M.; Leone, Stephen R.

2017-01-01

Semiconductor alloys containing silicon and germanium are of growing importance for compact and highly efficient photonic devices due to their favorable properties for direct integration into silicon platforms and wide tunability of optical parameters. Here, we report the simultaneous direct and energy-resolved probing of ultrafast electron and hole dynamics in a silicon-germanium alloy with the stoichiometry Si0.25Ge0.75 by extreme ultraviolet transient absorption spectroscopy. Probing the photoinduced dynamics of charge carriers at the germanium M4,5-edge (∼30 eV) allows the germanium atoms to be used as reporter atoms for carrier dynamics in the alloy. The photoexcitation of electrons across the direct and indirect band gap into conduction band (CB) valleys and their subsequent hot carrier relaxation are observed and compared to pure germanium, where the Ge direct (ΔEgap,Ge,direct=0.8 eV) and Si0.25Ge0.75 indirect gaps (ΔEgap,Si0.25Ge0.75,indirect=0.95 eV) are comparable in energy. In the alloy, comparable carrier lifetimes are observed for the X, L, and Γ valleys in the conduction band. A midgap feature associated with electrons accumulating in trap states near the CB edge following intraband thermalization is observed in the Si0.25Ge0.75 alloy. The successful implementation of the reporter atom concept for capturing the dynamics of the electronic bands by site-specific probing in solids opens a route to study carrier dynamics in more complex materials with femtosecond and sub-femtosecond temporal resolution. PMID:28653020

Ultraviolet absorption spectrum of HOCl

NASA Technical Reports Server (NTRS)

Burkholder, James B.

1993-01-01

The room temperature UV absorption spectrum of HOCl was measured over the wavelength range 200 to 380 nm with a diode array spectrometer. The absorption spectrum was identified from UV absorption spectra recorded following UV photolysis of equilibrium mixtures of Cl2O/H2O/HOCl. The HOCl spectrum is continuous with a maximum at 242 nm and a secondary peak at 304 nm. The measured absorption cross section at 242 nm was (2.1 +/- 0.3) x 10 exp -19/sq cm (2 sigma error limits). These results are in excellent agreement with the work of Knauth et al. (1979) but in poor agreement with the more recent measurements of Mishalanie et al. (1986) and Permien et al. (1988). An HOCl nu2 infrared band intensity of 230 +/- 35/sq cm atm was determined based on this UV absorption cross section. The present results are compared with these previous measurements and the discrepancies are discussed.

Impact of plasma jet vacuum ultraviolet radiation on reactive oxygen species generation in bio-relevant liquids

NASA Astrophysics Data System (ADS)

Jablonowski, H.; Bussiahn, R.; Hammer, M. U.; Weltmann, K.-D.; von Woedtke, Th.; Reuter, S.

2015-12-01

Plasma medicine utilizes the combined interaction of plasma produced reactive components. These are reactive atoms, molecules, ions, metastable species, and radiation. Here, ultraviolet (UV, 100-400 nm) and, in particular, vacuum ultraviolet (VUV, 10-200 nm) radiation generated by an atmospheric pressure argon plasma jet were investigated regarding plasma emission, absorption in a humidified atmosphere and in solutions relevant for plasma medicine. The energy absorption was obtained for simple solutions like distilled water (dH2O) or ultrapure water and sodium chloride (NaCl) solution as well as for more complex ones, for example, Rosewell Park Memorial Institute (RPMI 1640) cell culture media. As moderate stable reactive oxygen species, hydrogen peroxide (H2O2) was studied. Highly reactive oxygen radicals, namely, superoxide anion (O2•-) and hydroxyl radicals (•OH), were investigated by the use of electron paramagnetic resonance spectroscopy. All species amounts were detected for three different treatment cases: Plasma jet generated VUV and UV radiation, plasma jet generated UV radiation without VUV part, and complete plasma jet including all reactive components additionally to VUV and UV radiation. It was found that a considerable amount of radicals are generated by the plasma generated photoemission. From the experiments, estimation on the low hazard potential of plasma generated VUV radiation is discussed.

Enhancing Photocatalytic Activity on (MnO@TNTAs):Mn2+ with a Hierarchical Sandwich-Like Nanostructure via a Two-Step Procedure

NASA Astrophysics Data System (ADS)

Kong, Junhan; Zhang, Wei; Zhang, Yubo; Xia, Minghao; Wu, Xiuling; Wang, Yongqian

2018-02-01

Several semiconductor nanomaterial devices are increasingly being applied in a variety of fields, especially in the treating of environmental pollutants. We have fabricated (MnO@TNTAs):Mn2+ with sandwich-like nanostructures composed of TiO2 nanotube arrays (TNTAs), Mn-doped TNTAs and MnO. The experimental procedure was a two-step synthesis: first, using anodic oxidation methods and then hydrothermal methods. We carried out many characterizations of the "sandwiches" in the nanoscale. From the field emission scanning electron microscopy images we found nanofibers lying on the highly-ordered nanotube arrays. The diameter of the nanotubes was about 50 nm but the size of the nanofibers varied. Energy dispersive spectroscopy demonstrated that the nanofibers contained a manganese element and x-ray diffraction patterns showed the peak of the manganosite phase. From ultraviolet-visible light spectra, it was found that the nanostructures had strong absorption activities under both ultraviolet and visible light radiation, while pure TNTAs had absorption only under ultraviolet light. The photodegradation experiments proved that the sandwich-like nanostructures had an excellent photocatalytic activity (92.5% after 240 min), which was a great improvement compared with pure TNTAs. In this way, the structures as a device at the nanoscale have a huge potential in controlling environmental pollution.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gordon, I.M.; Pichakhchi, L.D.

It is shown that the emission spectrum of T Tauri stars with anomalous continuous radiation in the ultraviolet can be explained by assuming that it is a negative absorption spectrum of hydrogen excited by synchrotron radiation of great intensity in a small part of the star's atmosphere--in its active zone. A method was also proposed for the determination of the spectrum of synchrotron radiation from the observed hydrogen emission spectrum. The intensity in the infrared part of the spectrum was determined from the broadening of the higher terms of the Balmer series that form the quasicontinuum, while the intensity inmore » the ultraviolet was determined from hydrogen ionization. In the present study the distribution of hydrogen atoms among the excited levels in the field of such radiation is calculated using an electronic computer. The calculations show that the Balmer lines will in fact be observed in emission due to induced transitions, i.e., as a sequence of negative absorption lines. The considerable overpopulation of the upper levels is responsible for the small Balmer decrement and the appearance of anomalous emission in the ultraviolet and also for the increase in intensity of the latter when approaching the Balmer discontinuity. Thus the theory of the excitation of the emission spectrum of T Tauri stars is confirmed quantitatively. (auth)« less

Synthesis, Spectra, and Theoretical Investigations of 1,3,5-Triazines Compounds as Ultraviolet Rays Absorber Based on Time-Dependent Density Functional Calculations and three-Dimensional Quantitative Structure-Property Relationship.

PubMed

Wang, Xueding; Xu, Yilian; Yang, Lu; Lu, Xiang; Zou, Hao; Yang, Weiqing; Zhang, Yuanyuan; Li, Zicheng; Ma, Menglin

2018-03-01

A series of 1,3,5-triazines were synthesized and their UV absorption properties were tested. The computational chemistry methods were used to construct quantitative structure-property relationship (QSPR), which was used to computer aided design of new 1,3,5-triazines ultraviolet rays absorber compounds. The experimental UV absorption data are in good agreement with those predicted data using the Time-dependent density functional theory (TD-DFT) [B3LYP/6-311 + G(d,p)]. A suitable forecasting model (R > 0.8, P < 0.0001) was revealed. Predictive three-dimensional quantitative structure-property relationship (3D-QSPR) model was established using multifit molecular alignment rule of Sybyl program, which conclusion is consistent with the TD-DFT calculation. The exceptional photostability mechanism of such ultraviolet rays absorber compounds was studied and confirmed as principally banked upon their ability to undergo excited-state deactivation via an ultrafast excited-state proton transfer (ESIPT). The intramolecular hydrogen bond (IMHB) of 1,3,5-triazines compounds is the basis for the excited state proton transfer, which was explored by IR spectroscopy, UV spectra, structural and energetic aspects of different conformers and frontier molecular orbitals analysis.

Detection of ultraviolet radiation using tissue equivalent radiochromic gel materials

NASA Astrophysics Data System (ADS)

Bero, M. A.; Abukassem, I.

2009-05-01

Ferrous Xylenol-orange Gelatin gel (FXG) is known to be sensitive to ionising radiation such as γ and X-rays. The effect of ionising radiation is to produce an increase in the absorption over a wide region of the visible spectrum, which is proportional to the absorbed dose. This study demonstrates that FXG gel is sensitive to ultraviolet radiation and therefore it could functions as UV detector. Short exposure to UV radiation produces linear increase in absorption measured at 550nm, however high doses of UV cause the ion indicator colour to fad away in a manner proportional to the incident UV energy. Light absorbance increase at the rate of 1.1% per minute of irradiation was monitored. The exposure level at which the detector has linear response is comparable to the natural summer UV radiation. Evaluating the UV ability to pass through tissue equivalent gel materials shows that most of the UV gets absorbed in the first 5mm of the gel materials, which demonstrate the damaging effects of this radiation type on human skin and eyes. It was concluded that FXG gel dosimeter has the potential to offer a simple, passive ultraviolet radiation detector with sensitivity suitable to measure and visualises the natural sunlight UV exposure directly by watching the materials colour changes.

A new endstation at the Swiss Light Source for ultraviolet photoelectron spectroscopy, X-ray photoelectron spectroscopy, and X-ray absorption spectroscopy measurements of liquid solutions.

PubMed

Brown, Matthew A; Redondo, Amaia Beloqui; Jordan, Inga; Duyckaerts, Nicolas; Lee, Ming-Tao; Ammann, Markus; Nolting, Frithjof; Kleibert, Armin; Huthwelker, Thomas; Müächler, Jean-Pierre; Birrer, Mario; Honegger, Juri; Wetter, Reto; Wörner, Hans Jakob; van Bokhoven, Jeroen A

2013-07-01

A new liquid microjet endstation designed for ultraviolet (UPS) and X-ray (XPS) photoelectron, and partial electron yield X-ray absorption (XAS) spectroscopies at the Swiss Light Source is presented. The new endstation, which is based on a Scienta HiPP-2 R4000 electron spectrometer, is the first liquid microjet endstation capable of operating in vacuum and in ambient pressures up to the equilibrium vapor pressure of liquid water at room temperature. In addition, the Scienta HiPP-2 R4000 energy analyzer of this new endstation allows for XPS measurements up to 7000 eV electron kinetic energy that will enable electronic structure measurements of bulk solutions and buried interfaces from liquid microjet samples. The endstation is designed to operate at the soft X-ray SIM beamline and at the tender X-ray Phoenix beamline. The endstation can also be operated using a Scienta 5 K ultraviolet helium lamp for dedicated UPS measurements at the vapor-liquid interface using either He I or He II α lines. The design concept, first results from UPS, soft X-ray XPS, and partial electron yield XAS measurements, and an outlook to the potential of this endstation are presented.

Radiative transitions involving the (2p2)(3 Pe) metastable autodetaching of H(-)

NASA Technical Reports Server (NTRS)

Jacobs, V. L.; Bhatia, A. K.; Temkin, A.

1974-01-01

The absorption coefficient for the free-bound transition H (ls) + e(-)+ h omega yields H(-)(2 sq p,(3)P(e)) is calculated (together with the differential emission rate for the inverse process) using ls - 2s - 2p close coupling continuum wave functions and a Hylleraas bound state wave function. A maximum in the absorption and emission spectra is found to occur at a photon wavelength of 1219.5 A, which is 2 A closer to the Lyman alpha line than predicted by the calculations of Drake, and is in closer agreement with the stellar absorption feature identified by Heap and Stecher. The free-bound absorption process appears to be a significant source of continuous ultraviolet opacity.

Measuring the Local ISM along the Sight Lines of the Two Voyager Spacecraft with HST/STIS

NASA Astrophysics Data System (ADS)

Zachary, Julia; Redfield, Seth; Linsky, Jeffrey L.; Wood, Brian E.

2018-05-01

In 2012 August, Voyager 1 crossed the heliopause, becoming the first human-made object to exit the solar system. This milestone signifies the beginning of an important new era for local interstellar medium (LISM) exploration. We present measurements of the structure and composition of the LISM in the immediate path of the Voyager spacecraft by using high-resolution Hubble Space Telescope (HST) spectra of nearby stars that lie along the same lines of sight. We provide a comprehensive inventory of LISM absorption in the near-ultraviolet (2600–2800 Å) and far-ultraviolet (1200–1500 Å). The LISM absorption profiles are used to make comparisons between each pair of closely spaced (<15°) sight lines. With fits to several absorption lines, we make measurements of the physical properties of the LISM. We estimate electron density along the Voyager 2 sight line, and our values are consistent with recent measurements by Voyager 1. Excess absorption in the H I Lyα line displays the presence of both the heliosphere and an astrosphere around GJ 780. This is only the 14th detection of an astrosphere, and the large mass-loss rate (\\dot{M}=10 {\\dot{M}}ȯ ) is consistent with other subgiant stars. The heliospheric absorption matches the predicted strength for a sight line 58° from the upwind direction. As both HST and Voyager reach the end of their lifetimes, we have the opportunity to synthesize their respective observations, combining in situ measurements with the shortest possible line-of-sight measurements to study the Galactic ISM surrounding the Sun.

Design, fabrication, and measurement of two silicon-based ultraviolet and blue-extended photodiodes

NASA Astrophysics Data System (ADS)

Chen, Changping; Wang, Han; Jiang, Zhenyu; Jin, Xiangliang; Luo, Jun

2014-12-01

Two silicon-based ultraviolet (UV) and blue-extended photodiodes are presented, which were fabricated for light detection in the ultraviolet/blue spectral range. Stripe-shaped and octagon-ring-shaped structures were designed to verify parameters of the UV-responsivity, UV-selectivity, breakdown voltage, and response time. The ultra-shallow lateral pn junction had been successfully realized in a standard 0.5-μm complementary metal oxide semiconductor (CMOS) process to enlarge the pn junction area, enhance the absorption of UV light, and improve the responsivity and quantum efficiency. The test results illustrated that the stripe-shaped structure has the lower breakdown voltage, higher UV-responsicity, and higher UV-selectivity. But the octagon-ring-shaped structure has the lower dark current. The response time of both structures was almost the same.

Validation of Special Sensor Ultraviolet Limb Imager (SSULI) Ionospheric Tomography using ALTAIR Incoherent Scatter Radar Measurements

NASA Astrophysics Data System (ADS)

Dymond, K.; Nicholas, A. C.; Budzien, S. A.; Stephan, A. W.; Coker, C.; Hei, M. A.; Groves, K. M.

2015-12-01

The Special Sensor Ultraviolet Limb Imager (SSULI) instruments are ultraviolet limb scanning sensors flying on the Defense Meteorological Satellite Program (DMSP) satellites. The SSULIs observe the 80-170 nanometer wavelength range covering emissions at 91 and 136 nm, which are produced by radiative recombination of the ionosphere. We invert these emissions tomographically using newly developed algorithms that include optical depth effects due to pure absorption and resonant scattering. We present the details of our approach including how the optimal altitude and along-track sampling were determined and the newly developed approach we are using for regularizing the SSULI tomographic inversions. Finally, we conclude with validations of the SSULI inversions against ALTAIR incoherent scatter radar measurements and demonstrate excellent agreement between the measurements.

First-principles C band absorption spectra of SO2 and its isotopologues

NASA Astrophysics Data System (ADS)

Jiang, Bin; Kumar, Praveen; Kłos, Jacek; Alexander, Millard H.; Poirier, Bill; Guo, Hua

2017-04-01

The low-energy wing of the C ˜ B12 ←X˜ 1A1 absorption spectra for SO2 in the ultraviolet region is computed for the 32S,33S,34S and 36S isotopes, using the recently developed ab initio potential energy surfaces (PESs) of the two electronic states and the corresponding transition dipole surface. The state-resolved absorption spectra from various ro-vibrational states of SO2(X˜ 1A1 ) are computed. When contributions of these excited ro-vibrational states are included, the thermally averaged spectra are broadened but maintain their key characters. Excellent agreement with experimental absorption spectra is found, validating the accuracy of the PESs. The isotope shifts of the absorption peaks are found to increase linearly with energy, in good agreement with experiment.

Low-redshift Lyman-alpha absorption lines and the dark matter halos of disk galaxies

NASA Technical Reports Server (NTRS)

Maloney, Philip

1992-01-01

Ultraviolet observations of the low-redshift quasar 3C 273 using the Hubble Space Telescope have revealed many more Lyman-alpha absorption lines than would be expected from extrapolation of the absorption systems seen toward QSOs at z about 2. It is shown here that these absorption lines can plausibly be produced by gas at large radii in the disks of spiral and irregular galaxies; the gas is confined by the dark matter halos and ionized and heated by the extragalactic radiation field. This scenario does not require the extragalactic ionizing radiation field to decline as rapidly with decreasing z as the QSO emissivity. Observations of Ly-alpha absorption through the halos of known galaxies at low redshift will constrain both the extragalactic background and the properties of galactic halos.

Local Interstellar Medium. International Astronomical Union Colloquium No. 81

NASA Technical Reports Server (NTRS)

Kondo, Y. (Editor); Bruhweiler, F. C. (Editor); Savage, B. D. (Editor)

1984-01-01

Helium and hydrogen backscattering; ultraviolet and EUV absorption spectra; optical extinction and polarization; hot gases; soft X-ray observations; infrared and millimeter wavelengths; radio wavelengths and theoretical models of the interstellar matter within about 150 parsecs of the Sun were examined.

DIODE-LASER-BASED ULTRAVIOLET ABSORPTION SENSOR FOR NITRIC OXIDE. (R828180)

EPA Science Inventory

The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Concl...

INTERNAL FILTERS: PROSPECTS FOR UV-ACCLIMATION IN HIGHER PLANTS

EPA Science Inventory

Wavelength-selective absorption of solar radiation within plant leaves allows penetration of visible radiation (400-700nm) to the chloroplasts, while removing much of the damaging ultraviolet-B (UV-B, 280-320 nm) radiation. Flavonoids are important in this wavelength-selective ab...

High-resolution absorption cross sections of carbon monoxide bands at 295 K between 91.7 and 100.4 nanometers

NASA Technical Reports Server (NTRS)

Stark, G.; Yoshino, K.; Smith, Peter L.; Ito, K.; Parkinson, W. H.

1991-01-01

Theoretical descriptions of the abundance and excitation of carbon monoxide in interstellar clouds require accurate data on the vacuum-ultraviolet absorption spectrum of the molecule. The 6.65 m spectrometer at the Photon Factory synchrotron light source was used to measure photoabsorption cross sections of CO features between 91.2 and 100.4 nm. These data were recorded at a resolving power of 170,000, more than 20 times greater than that used in previous work.

Determination of sulfur trioxide in engine exhaust.

PubMed Central

Arnold, D R

1975-01-01

Sulfur trioxide in the exhaust gas of an internal combustion engine is removed and concentrated by absorption in a solution of 80% isopropyl alcohol, which quantitatively absorbs it and inhibits the oxidation of any sulfur dioxide which may be absorbed. The absorbed sulfur trioxide (sulfuric acid) is determined by an absorption titration by using barium chloride as the titrant and thorin as the indicator. The sulfur dioxide content of the exhaust is measured continuously by means of a DuPont Model 411 ultraviolet photoanalyzer. PMID:50930

Non-LTE H2+ as the source of missing opacity in the solar atmosphere

NASA Technical Reports Server (NTRS)

Swamy, K. S. K.; Stecher, T. P.

1974-01-01

The population of the various vibrational levels of the H2+ molecule has been calculated from the consideration of formation and destruction mechanisms. The resulting population is used in calculating the total absorption due to H2+ and is compared with the other known sources of opacity at several optical depths of the solar atmosphere. It is shown that the absorption due to H2+ can probably account for the missing ultraviolet opacity in the solar atmosphere.

Thin film coatings for improved alpha/epi

NASA Technical Reports Server (NTRS)

Krisl, M. E.; Sachs, I. M.

1985-01-01

New thin film coatings were developed for fused silica, ceria doped glass, and Corning 0211 microsheet which provide increased emissivity and/or decreased solar absorption. Emissivity is enhanced by suppression of the reststrahlen reflectance and solar absorption is reduced by externally reflecting the ultraviolet portion of the solar spectrum. Optical properties of these coatings make them suitable for both solar cell cover and thermal control mirror applications. Measurements indicate equivalent environmental performance to conventional solar cell cover and thermal control mirror products.

Substitution determination of Fmoc-substituted resins at different wavelengths.

PubMed

Eissler, Stefan; Kley, Markus; Bächle, Dirk; Loidl, Günther; Meier, Thomas; Samson, Daniel

2017-10-01

In solid-phase peptide synthesis, the nominal batch size is calculated using the starting resin substitution and the mass of the starting resin. The starting resin substitution constitutes the basis for the calculation of a whole set of important process parameters, such as the number of amino acid derivative equivalents. For Fmoc-substituted resins, substitution determination is often performed by suspending the Fmoc-protected starting resin in 20% (v/v) piperidine in DMF to generate the dibenzofulvene-piperidine adduct that is quantified by ultraviolet-visible spectroscopy. The spectrometric measurement is performed at the maximum absorption wavelength of the dibenzofulvene-piperidine adduct, that is, at 301.0 nm. The recorded absorption value, the resin weight and the volume are entered into an equation derived from Lambert-Beer's law, together with the substance-specific molar absorption coefficient at 301.0 nm, in order to calculate the nominal substitution. To our knowledge, molar absorption coefficients between 7100 l mol -1  cm -1 and 8100 l mol -1  cm -1 have been reported for the dibenzofulvene-piperidine adduct at 301.0 nm. Depending on the applied value, the nominal batch size may differ up to 14%. In this publication, a determination of the molar absorption coefficients at 301.0 and 289.8 nm is reported. Furthermore, proof is given that by measuring the absorption at 289.8 nm the impact of wavelength accuracy is reduced. © 2017 The Authors Journal of Peptide Science published by European Peptide Society and John Wiley & Sons Ltd. © 2017 The Authors Journal of Peptide Science published by European Peptide Society and John Wiley & Sons Ltd.

Determination of polycyclic aromatic hydrocarbons and their nitro-, amino-derivatives absorbed on particulate matter 2.5 by multiphoton ionization mass spectrometry using far-, deep-, and near-ultraviolet femtosecond lasers.

PubMed

Tang, Yuanyuan; Imasaka, Tomoko; Yamamoto, Shigekazu; Imasaka, Totaro

2016-06-01

Multiphoton ionization processes of parent-polycyclic aromatic hydrocarbons (PPAHs), nitro-PAHs (NPAHs), and amino-PAHs (APAHs) were examined by gas chromatography combined with time-of-flight mass spectrometry using a femtosecond Ti:sapphire laser as the ionization source. The efficiency of multiphoton ionization was examined using lasers emitting in the far-ultraviolet (200 nm), deep-ultraviolet (267 nm), and near-ultraviolet (345 nm) regions. The largest signal intensities were obtained when the far-ultraviolet laser was employed. This favorable result can be attributed to the fact that these compounds have the largest molar absorptivities in the far-ultraviolet region. On the other hand, APAHs were ionized more efficiently than NPAHs in the near-ultraviolet region because of their low ionization energies. A sample extracted from a real particulate matter 2.5 (PM2.5) sample was measured, and numerous signal peaks arising from PAH and its analogs were observed at 200 nm. On the other hand, only a limited number of signed peaks were observed at 345 nm, some of which were signed to PPAHs, NPAHs, and APAHs. Thus, multiphoton ionization mass spectrometry has potential for the use in comprehensive analysis of toxic environmental pollutants. Copyright © 2016 Elsevier Ltd. All rights reserved.

[Rapid analysis of metronidazole tablets by optic-fiber sensing technologies and the similarity of ultraviolet spectra].

PubMed

Jin, Lu; Li, Li; Li, Xin-xia; Yang, Ting; Kong, Bin; Xu, Ping-ping

2011-02-01

The paper is to report the development of an optic-fiber sensing technology method to analyze metronidazole tablets rapidly. In this fiber-optic sensing system, the light from source delivering to probe can be dipped into simple-handling sample solution, absorbed by the solution and reflected to the fiber-optic and detected in the detection system at last. Then the drug content can be shown in the screen from the ultraviolet absorption spectra and the consistency between that obtained by this method and that in China Pharmacopoeia can be compared. With regard to data processing, a new method is explored to identify the authenticity of drugs using the similarity between the sample map and the standard pattern by full ultraviolet spectrum. The results indicate that ultraviolet spectra of tablets can be obtained from this technology and the determination results showed no significant difference as compared with the method in China Pharmacopoeia (P > 0.05), and the similarity can be a parameter to identify the authenticity of drugs.

Ultraviolet Spectra of Two Magnetic White Dwarfs and Ultraviolet Spectra of Subluminous Objects Found in the Kiso Schmidt Survey and Ultraviolet Absorptions in the Spectra of DA White Dwarfds

NASA Technical Reports Server (NTRS)

Wegner, Gary A.

1988-01-01

Research under NASA Grant NAG5-287 has carried out a number of projects in conjunction with the International Ultraviolet Explorer (IUE) satellite. These include: (1) studies of the UV spectra of DA white dwarfs which show quasi-molecular bands of H2 and H2(+); (2) the peculiar star HR6560; (3) the UV spectra of two magnetic white dwarfs that also show the quasi-molecular features; (4) investigations of the UV spectra of subluminous stars, primarily identified from visual wavelength spectroscopy in the Kiso survey of UV excess stars, some of which show interesting metal lines in their UV spectra; and (5) completion of studies of UV spectra of DB stars. The main result of this research has been to further knowledge of the structure and compositions of subluminous stars which helps cast light on their formation and evolution.

Ultraviolet Changes of the Central Source and the Very Nearby Ejecta

NASA Technical Reports Server (NTRS)

Gull, Theodore R.; Nielsen, Krister; Vierira, Gladys; Hillier, John; Walborn, Nolan; Davidson, Kris

2004-01-01

We utilized the high spatial and high spectral resolution of the HST/STIS MAMA echelle modes in the ultraviolet (0.025 inch spatial resolution and 30,000 to 120,000 spectral resolving power) to view changes in and around Eta Carinae before and after the X-Ray drop which occurred on June 29, 2003 (M. Corcoran, IAUC 8160). Major changes in the spectra of the Central Source and nearby nebulosities occurred between June 22 and July 5. Visibility of the Central Source dropped, especially between 1175 and 1350 Angstroms, but not uniformly throughout the ultraviolet. This fading is likely due to multiple line absorptions both in the source and in the intervening ejecta. Nebular emission of Si III] and Fe III, located 0.09 sec. to the west, disappeared. By July 29, a bright feature extending up to 0.071 sec. east of the Central Source became prominent in broad emission lines near 2500 Angstroms, but was not noticeable longward of 2900 Angstroms. ACS/HRC imagery and STIS CCD spectra taken concurrently are being examined for larger scale changes. Numerous narrow velocity components between -146 and -585 kilometers per second were identified in spectra before the minimum. New components appeared primarily in Fe II absorption lines with velocities between -170 and -380 kilometers per second. While the lines of the -513 kilometers per second component did not change, most lines of the -146 kilometers per second component changed considerably. Lines originating from high energy levels diminished or disappeared, while lines originating from lower energy levels strengthened. Strong absorption lines of Ti II, not present before the X-Ray drop, appeared within seven days, but disappeared by July 29. Further analysis of these unprecedented data will provide significant new information about the structure of Eta Carinae and its periodic variations.

Bombyx mori silk protein films microprocessing with a nanosecond ultraviolet laser and a femtosecond laser workstation: theory and experiments

NASA Astrophysics Data System (ADS)

Lazare, S.; Sionkowska, A.; Zaborowicz, M.; Planecka, A.; Lopez, J.; Dijoux, M.; Louména, C.; Hernandez, M.-C.

2012-01-01

Laser microprocessing of several biopolymers from renewable resources is studied. Three proteinic materials were either extracted from the extracellular matrix like Silk Fibroin/Sericin and collagen, or coming from a commercial source like gelatin. All can find future applications in biomedical experimentation, in particular for cell scaffolding. Films of ˜hundred of microns thick were made by aqueous solution drying and laser irradiation. Attention is paid to the properties making them processable with two laser sources: the ultraviolet and nanosecond (ns) KrF (248 nm) excimer and the infrared and femtosecond (fs) Yb:KGW laser. The UV radiation is absorbed in a one-photon resonant process to yield ablation and the surface foaming characteristics of a laser-induced pressure wave. To the contrary, resonant absorption of the IR photons of the fs laser is not possible and does not take place. However, the high field of the intense I>˜1012 W/cm2 femtosecond laser pulse ionizes the film by the multiphoton absorption followed by the electron impact mechanism, yielding a dense plasma capable to further absorb the incident radiation of the end of the pulse. The theoretical model of this absorption is described in detail, and used to discuss the presented experimental effects (cutting, ablation and foaming) of the fs laser. The ultraviolet laser was used to perform simultaneous multiple spots experiments in which energetic foaming yields melt ejection and filament spinning. Airborne nanosize filaments "horizontally suspended by both ends" (0.25 μm diameter and 10 μm length) of silk biopolymer were observed upon irradiation with large fluences.

Dual-wavelength light-emitting diode-based ultraviolet absorption detector for nano-flow capillary liquid chromatography.

PubMed

Xie, Xiaofeng; Tolley, Luke T; Truong, Thy X; Tolley, H Dennis; Farnsworth, Paul B; Lee, Milton L

2017-11-10

The design of a miniaturized LED-based UV-absorption detector was significantly improved for on-column nanoflow LC. The detector measures approximately 27mm×24mm×10mm and weighs only 30g. Detection limits down to the nanomolar range and linearity across 3 orders of magnitude were obtained using sodium anthraquinone-2-sulfonate as a test analyte. Using two miniaturized detectors, a dual-detector system was assembled containing 255nm and 275nm LEDs with only 216nL volume between the detectors A 100μm slit was used for on-column detection with a 150μm i.d. packed capillary column. Chromatographic separation of a phenol mixture was demonstrated using the dual-detector system, with each detector producing a unique chromatogram. Less than 6% variation in the ratios of absorbances measured at the two wavelengths for specific analytes was obtained across 3 orders of magnitude concentration, which demonstrates the potential of using absorption ratio measurements for target analyte detection. The dual-detector system was used for simple, but accurate, mobile phase flow rate measurement at the exit of the column. With a flow rate range from 200 to 2000nL/min, less than 3% variation was observed. Copyright © 2017 Elsevier B.V. All rights reserved.

Attosecond transient absorption instrumentation for thin film materials: Phase transitions, heat dissipation, signal stabilization, timing correction, and rapid sample rotation.

PubMed

Jager, Marieke F; Ott, Christian; Kaplan, Christopher J; Kraus, Peter M; Neumark, Daniel M; Leone, Stephen R

2018-01-01

We present an extreme ultraviolet (XUV) transient absorption apparatus tailored to attosecond and femtosecond measurements on bulk solid-state thin-film samples, specifically when the sample dynamics are sensitive to heating effects. The setup combines methodology for stabilizing sub-femtosecond time-resolution measurements over 48 h and techniques for mitigating heat buildup in temperature-dependent samples. Single-point beam stabilization in pump and probe arms and periodic time-zero reference measurements are described for accurate timing and stabilization. A hollow-shaft motor configuration for rapid sample rotation, raster scanning capability, and additional diagnostics are described for heat mitigation. Heat transfer simulations performed using a finite element analysis allow comparison of sample rotation and traditional raster scanning techniques for 100 Hz pulsed laser measurements on vanadium dioxide, a material that undergoes an insulator-to-metal transition at a modest temperature of 340 K. Experimental results are presented confirming that the vanadium dioxide (VO 2 ) sample cannot cool below its phase transition temperature between laser pulses without rapid rotation, in agreement with the simulations. The findings indicate the stringent conditions required to perform rigorous broadband XUV time-resolved absorption measurements on bulk solid-state samples, particularly those with temperature sensitivity, and elucidate a clear methodology to perform them.

Attosecond transient absorption instrumentation for thin film materials: Phase transitions, heat dissipation, signal stabilization, timing correction, and rapid sample rotation

NASA Astrophysics Data System (ADS)

Jager, Marieke F.; Ott, Christian; Kaplan, Christopher J.; Kraus, Peter M.; Neumark, Daniel M.; Leone, Stephen R.

2018-01-01

We present an extreme ultraviolet (XUV) transient absorption apparatus tailored to attosecond and femtosecond measurements on bulk solid-state thin-film samples, specifically when the sample dynamics are sensitive to heating effects. The setup combines methodology for stabilizing sub-femtosecond time-resolution measurements over 48 h and techniques for mitigating heat buildup in temperature-dependent samples. Single-point beam stabilization in pump and probe arms and periodic time-zero reference measurements are described for accurate timing and stabilization. A hollow-shaft motor configuration for rapid sample rotation, raster scanning capability, and additional diagnostics are described for heat mitigation. Heat transfer simulations performed using a finite element analysis allow comparison of sample rotation and traditional raster scanning techniques for 100 Hz pulsed laser measurements on vanadium dioxide, a material that undergoes an insulator-to-metal transition at a modest temperature of 340 K. Experimental results are presented confirming that the vanadium dioxide (VO2) sample cannot cool below its phase transition temperature between laser pulses without rapid rotation, in agreement with the simulations. The findings indicate the stringent conditions required to perform rigorous broadband XUV time-resolved absorption measurements on bulk solid-state samples, particularly those with temperature sensitivity, and elucidate a clear methodology to perform them.

A new model for Mars atmospheric dust based upon analysis of ultraviolet through infrared observations from Mariner 9, Viking, and Phobos

NASA Technical Reports Server (NTRS)

Clancy, R. T.; Lee, S. W.; Gladstone, G. R.; Mcmillan, W. W.; Rousch, T.

1995-01-01

We propose key modifications to the Toon et al. (1977) model of the particle size distribution and composition of Mars atmospheric dust, based on a variety of spacecraft and wavelength observations of the dust. A much broader (r(sub eff) variance approximately 0.8 micrometers), smaller particle size (r(sub mode) approximately 0.02 micrometers) distribution coupled with a 'palagonite-like' composition is argued to fit the complete ultraviolet-to-30-micrometer absorption properties of the dust better than the montmorillonite-basalt, r(sub eff) variance = 0.4 micrometers, r(sub mode) = 0.40 dust model of Toon et al. Mariner 9 (infrared interferometer spectrometer) IRIS spectra of high atmospheric dust opacities during the 1971-1972 Mars global dust storm are analyzed in terms of the Toon et al. dust model, and a Hawaiian palagonite sample (Rousch et al., 1991) with two different size distribution models incorporating smaller dust particle sizes. Viking Infrared Thermal Mapper (IRTM) emmission-phase-function (EPF) observations at 9 micrometers are analyzed to retrieve 9-micrometer dust opacities coincident with solar band dust opacities obtained from the same EPF sequences (Clancy and Lee, 1991). These EPF dust opacities provide an independent measurement of the visible/9-micrometer extinction opacity ratio (greater than or = 2) for Mars atmospheric dust, which is consistent with a previous measurement by Martin (1986). Model values for the visible/9-micrometer opacity ratio and the ultraviolet and visible single-scattering albedos are calculated for the palagonite model with the smaller particle size distributions compared to the same properties for the Toon et al. model of dust. The montmorillonite model of the dust is found to fit the detailed shape of the dust 9-micrometer absorption well. However, it predicts structured, deep aborptions at 20 micrometers which are not observed and requires a separate ultraviolet-visible absorbing component to match the observed behavior of the dust in this wavelength region. The modeled palagonite does not match the 8-to 9-micrometer absorption presented by the dust in the IRIS spectra, probably due to its low SiO2 content (31%). However, it does provide consistent levels of ultraviolet/visible absorption, 9-to 12-micrometer absorption, and a lack of structured absorption at 20 micrometers. The ratios of dust extinction opacities at visible, 9 micrometers, and 30 micrometers are strongly affected by the dust particle size distribution. The Toon et al. dust size distribution (r(sub mode) = 0.40,r(sub eff) variance = 0.4 micrometers, r(sub cwmu) = 2.7 micrometers) predicts the correct ratio of the 9- to 30-micrometer opacity, but underpredicts the visible/9-micrometer opacity ratio considerably (1 versus greater than or = 2). A similar particle distribution width with smaller particle sizes (r(sub mode) = 0.17, r(sub eff) variance = 0.4 micrometers, r(sub cwmu) = 1.2 micrometers) will fit the observed visible/9-micrometer opacity ratio, but overpredicts the observed 9-micrometer/30-micrometer opacity ratio. A smaller and much broader particle size distribution (r(sub mode) = 0.002, r(sub eff) variance = 0.8 micrometers, r(sub cwmu) = 1.8 micrometers) can fit both dust opacity ratios. Overall, the nanocrystalline structure of palagonite coupled with a smaller, broader distribution of dust particle sizes provides a more consistent fit than the Toon et al. model of the dust to the IRIS spectra, the observed visible/9-micrometer dust opacity ratio, the Phobos occulation measurements of the dust particle sizes (Chassefiere et al., 1992), and the weakness of surface near IR absorptions expected for clay minerals (Clark, 1992; Bell and Crisp, 1993).

The Ultraviolet Spectrograph (UVS) on Juno

NASA Astrophysics Data System (ADS)

Gladstone, G. R.; Persyn, S.; Eterno, J.; Slater, D. C.; Davis, M. W.; Versteeg, M. H.; Persson, K. B.; Siegmund, O. H.; Marquet, B.; Gerard, J.; Grodent, D. C.

2008-12-01

Juno, a NASA New Frontiers mission, plans for launch in August 2011, a 5-year cruise (including a flyby of Earth in October 2013 for a gravity boost), and 14 months around Jupiter after arriving in August 2016. The spinning (2 RPM), solar-powered Juno will study Jupiter from a highly elliptical orbit, in which the spacecraft (for about 6 hours once every 11 days) dives down over the north pole, skims the outermost atmosphere, and rises back up over the south pole. This orbit allows Juno avoid most of the intense particle radiation surrounding the planet and provides an excellent platform for investigating Jupiter's polar magnetosphere. Part of the exploration of Jupiter's polar magnetosphere will involve remote sensing of the far-ultraviolet H and H2 auroral emissions, plus gases such as methane and acetylene which add their absorption signature to the H2 emissions. This hydrocarbon absorption can be used to estimate the energy of the precipitating electrons; since more energetic electrons penetrate deeper into the atmosphere and the UV emissions they produce will show more absorption. Juno will carry an Ultraviolet Spectrograph (UVS) to make spectral images of Jupiter's aurora. UVS is a UV imaging spectrograph sensitive to both extreme and far ultraviolet emissions in the 70-205~nm range that will characterize the morphology and spectral nature of Jupiter's auroral emissions. Juno UVS consists of two separate sections: a dedicated telescope/spectrograph assembly and a vault electronics box. The telescope/spectrograph assembly contains a telescope which feeds a 0.15-m Rowland circle spectrograph. The telescope has an input aperture 40×40~mm2 and uses an off-axis parabolic primary mirror. A flat scan mirror situated at the front end of the telescope (used to target specific auroral features at up to ±30° perpendicular to the Juno spin plane) directs incoming light to the primary. The light is then focused onto the spectrograph entrance slit, which has a 'dog- bone' shape 6° long, in three 2° sections of 0.2°, 0.05°, and 0.2° width (projected onto the sky). Light entering the slit is dispersed by a toroidal grating which focuses the UV bandpass onto a curved microchannel plate (MCP) cross delay line (XDL) detector with a solar blind UV- sensitive CsI photocathode, which makes up the instrument's focal plane. Tantalum shielding surrounds the detector assembly to protect the detector and the adjacent detector electronics from high-energy electrons. The main electronics box is located in the Juno vault. Inside are two redundant high-voltage power supplies (HVPS), two redundant low-voltage power supplies, the command and data handling (C&DH) electronics, heater/actuator activation electronics, scan mirror electronics, and event processing electronics. An overview of the UVS design and scientific performance will be presented.

Free-electron laser wavelength-selective materials alteration and photoexcitation spectroscopy

NASA Astrophysics Data System (ADS)

Tolk, N. H.; Albridge, R. G.; Barnes, A. V.; Barnes, B. M.; Davidson, J. L.; Gordon, V. D.; Margaritondo, G.; McKinley, J. T.; Mensing, G. A.; Sturmann, J.

1996-10-01

The free-electron laser (FEL) has become an important tool for producing high-intensity photon beams, especially in the infrared. Synchrotron radiation's primary spectral domains are in the ultraviolet and X-ray region. FEL's are therefore excellent complimentary facilities to synchrotron radiation sources. While FEL's have seen only limited use in experimentation, recently developed programs at Vanderbilt University in Nashville, TN, are swiftly rectifying this situation. This review paper examines practical experience obtained through pioneering programs using the Vanderbilt FEL, which currently hosts one of the largest FEL materials research programs. Results will be discussed in three areas: two-photon absorption in germanium, FEL-assisted internal photoemission measurements of interface energy barriers (FELIPE), and wavelength-specific laser diamond ablation.

Development of KRISS standard reference photometer (SRP) for ambient ozone measurement

NASA Astrophysics Data System (ADS)

Lee, S.; Lee, J.

2014-12-01

Surface ozone has adverse impacts on human health and ecosystem. Accurate measurement of ambient ozone concentration is essential for developing effective mitigation strategies and understanding atmospheric chemistry. Korea Research Institute of Standards and Science (KRISS) has developed new ozone standard reference photometers (SRPs) for the calibration of ambient ozone instruments. The basic principle of the KRISS ozone SRPs is to determine the absorption of ultraviolet radiation at a specific wavelength, 253.7 nm, by ozone in the atmosphere. Ozone concentration is calculated by converting UV transmittance through the Beer-Lambert Law. This study introduces the newly developed ozone SRPs and characterizes their performance through uncertainty analysis and comparison with BIPM (International Bureau of Weights and Measures) SRP.

40 CFR 1065.1010 - Reference materials.

Code of Federal Regulations, 2010 CFR

2010-07-01

... § 1065.1010—Institute of Petroleum Materials Document No. and name Part 1065 reference IP-470... atomic absorption spectrometry 1065.705 IP-500, Determination of the phosphorus content of residual fuels by ultra-violet spectrometry 1065.705 IP-501, Determination of aluminum, silicon, vanadium, nickel...

Middle Atmosphere Program. Handbook for MAP, volume 8

NASA Technical Reports Server (NTRS)

Sechrist, C. F., Jr. (Editor)

1983-01-01

Various investigations relative to middle atmosphere research are discussed. Atmospheric warming periods in 1982-83, atmospheric composition, the comparison of irradiance measurement calibration, and molecular absorption processes related to the penetration of ultraviolet solar radiation into the middle atmosphere, are among the topics discussed.

Direct and simultaneous observation of ultrafast electron and hole dynamics in germanium

DOE PAGES

Zurch, Michael; Chang, Hung -Tzu; Borja, Lauren J.; ...

2017-06-01

Understanding excited carrier dynamics in semiconductors is crucial for the development of photovoltaics and efficient photonic devices. However, overlapping spectral features in optical pump-probe spectroscopy often render assignments of separate electron and hole carrier dynamics ambiguous. Here, ultrafast electron and hole dynamics in germanium nanocrystalline thin films are directly and simultaneously observed by ultrafast transient absorption spectroscopy in the extreme ultraviolet at the germanium M 4,5 edge. We decompose the spectra into contributions of electronic state blocking and photo-induced band shifts at a carrier density of 8 × 10 20 cm –3. Separate electron and hole relaxation times are observedmore » as a function of hot carrier energies. A first-order electron and hole decay of ~1 ps suggests a Shockley–Read–Hall recombination mechanism. Furthermore, the simultaneous observation of electrons and holes with extreme ultraviolet transient absorption spectroscopy paves the way for investigating few- to sub-femtosecond dynamics of both holes and electrons in complex semiconductor materials and across junctions.« less

Protective effect of cerium ion against ultraviolet B radiation-induced water stress in soybean seedlings.

PubMed

Mao, Chun Xia; Chen, Min Min; Wang, Lei; Zou, Hua; Liang, Chan Juan; Wang, Li Hong; Zhou, Qing

2012-06-01

Effects of cerium ion (Ce(III)) on water relations of soybean seedlings (Glycine max L.) under ultraviolet B radiation (UV-B, 280-320 nm) stress were investigated under laboratory conditions. UV-B radiation not only affected the contents of two osmolytes (proline, soluble sugar) in soybean seedlings, but also inhibited the transpiration in soybean seedlings by decreasing the stomatal density and conductance. The two effects caused the inhibition in the osmotic and metabolic absorption of water, which decreased the water content and the free water/bound water ratio. Obviously, UV-B radiation led to water stress, causing the decrease in the photosynthesis in soybean seedlings. The pretreatment with 20 mg L(-1) Ce(III) could alleviate UV-B-induced water stress by regulating the osmotic and metabolic absorption of water in soybean seedlings. The alleviated effect caused the increase in the photosynthesis and the growth of soybean seedlings. It is one of the protective effect mechanisms of Ce(III) against the UV-B radiation-induced damage to plants.

Evaluation of thermal control coatings for use on solar dynamic radiators in low earth orbit

NASA Technical Reports Server (NTRS)

Dever, Joyce A.; Rodriguez, Elvin; Slemp, Wayne S.; Stoyack, Joseph E.

1991-01-01

Thermal control coatings with high thermal emittance and low solar absorptance are needed for Space Station Freedom (SSF) solar dynamic power module radiator (SDR) surfaces for efficient heat rejection. Additionally, these coatings must be durable to low earth orbital (LEO) environmental effects of atomic oxygen, ultraviolet radiation and deep thermal cycles which occur as a result of start-up and shut-down of the solar dynamic power system. Eleven candidate coatings were characterized for their solar absorptance and emittance before and after exposure to ultraviolet (UV) radiation (200 to 400 nm), vacuum UV (VUV) radiation (100 to 200 nm) and atomic oxygen. Results indicated that the most durable and best performing coatings were white paint thermal control coatings Z-93, zinc oxide pigment in potassium silicate binder, and YB-71, zinc orthotitanate pigment in potassium silicate binder. Optical micrographs of these materials exposed to the individual environmental effects of atomic oxygen and vacuum thermal cycling showed that no surface cracking occurred.

Synthesis, crystal structure, photophysical properties and theoretical studies of a novel bis(phenylisoxazolyl) benzene derivative

NASA Astrophysics Data System (ADS)

de Brito, A. C. F.; Correa, R. S.; Pinto, A. A.; Matos, M. J. S.; Tenorio, J. C.; Taylor, J. G.; Cazati, T.

2018-07-01

Isoxazoles have well established biological activities but, have been underexplored as synthetic intermediates for applications in materials science. The aims of this work are to synthesis a novel isoxazole and analyze its structural and photophysical properties for application in electronic organic materials. The novel bis (phenylisoxazolyl) benzene compound was synthesized in four steps and characterized by NMR, high resolution mass spectrometry, differential thermal analysis, infrared spectroscopy, cyclic voltammetry, ultraviolet-visible spectroscopy, fluorescence spectroscopy, DFT and TDDFT calculations. The molecule presented optical absorption in the ultraviolet region (from 290 nm to 330 nm), with maximum absorption length centered at 306 nm. The molar extinction coefficients (ε), fluorescence emission spectra and quantum efficiencies in chloroform and dimethylformamide solution were determined. Cyclic voltammetry analysis was carried out for estimating the HOMO energy level and these properties make it desirable material for photovoltaic device applications. Finally, the excited-state properties of present compound were calculated by time-dependent density functional theory (TDDFT).

Validation of an analytical method for the quantitative determination of selenium in bacterial biomass by ultraviolet-visible spectrophotometry.

PubMed

Mörschbächer, Ana Paula; Dullius, Anja; Dullius, Carlos Henrique; Bandt, Cassiano Ricardo; Kuhn, Daniel; Brietzke, Débora Tairini; Malmann Kuffel, Fernando José; Etgeton, Henrique Pretto; Altmayer, Taciélen; Gonçalves, Tamara Engelmann; Oreste, Eliézer Quadro; Ribeiro, Anderson Schwingel; de Souza, Claucia Fernanda Volken; Hoehne, Lucélia

2018-07-30

The present paper describes the validation of a spectrophotometry method involving molecular absorption in the visible ultraviolet-visible (UV-Vis) region for selenium (Se) determination in the bacterial biomass produced by lactic acid bacteria (LAB). The method was found to be suitable for the target application and presented a linearity range from 0.025 to 0.250 mg/L Se. The angular and linear coefficients of the linear equation were 1.0678 and 0.0197 mg/L Se, respectively, and the linear correlation coefficient (R 2 ) was 0.9991. Analyte recovery exceeded 96% with a relative standard deviation (RSD) below 3%. The Se contents in LAB ranged from 0.01 to 20 mg/g. The Se contents in the bacterial biomass determined by UV-Vis were not significantly different (p > 0.05) those determined by graphite furnace atomic absorption spectrometry. Thus, Se can be quantified in LAB biomass using this relatively simpler technique. Copyright © 2018 Elsevier Ltd. All rights reserved.

UV Timing and Spectroscopy of the Crab Nebula Pulsar

NASA Technical Reports Server (NTRS)

Gull, Theodore R.; Lunqvist, Peter; Sollerman, Jesper; Lindler, Don; Fisher, Richard R. (Technical Monitor)

2001-01-01

We have used the Hubble Space Telescope and Space Telescope Imaging Spectrograph to obtain Near Ultraviolet (NUV) (1600-3200 Angstroms) and Far Ultraviolet (FUV) (1140-1720 Angstroms) spectra and pulse profiles of the Crab Nebula's pulsar. The pulse period agrees well with the radio predictions. The NUV and FUV pulse profiles are little changed from the visible wavelength profile. Spectra obtained with the Nordic Optical Telescope were combined with the UV spectra for full coverage from 1140-9250Angstoms. Dereddening the spectrum with a standard extinction curve achieves a flat spectrum for E(B-V)=0.52, R=3.1. Lyman alpha absorption indicates a column density of 3.0=/-0.5 x 10(exp 21) cm -2, consistent with the E(B-V) of 0.52. The dereddened spectrum can be fitted by a power law with spectral index alpha=0.11+/-0.04. A broad, blueshifted absorption is seen in CIV (1550Angstroms), reaching a velocity of about 2500 kilometer per second.

Direct and simultaneous observation of ultrafast electron and hole dynamics in germanium

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zurch, Michael; Chang, Hung -Tzu; Borja, Lauren J.

Understanding excited carrier dynamics in semiconductors is crucial for the development of photovoltaics and efficient photonic devices. However, overlapping spectral features in optical pump-probe spectroscopy often render assignments of separate electron and hole carrier dynamics ambiguous. Here, ultrafast electron and hole dynamics in germanium nanocrystalline thin films are directly and simultaneously observed by ultrafast transient absorption spectroscopy in the extreme ultraviolet at the germanium M 4,5 edge. We decompose the spectra into contributions of electronic state blocking and photo-induced band shifts at a carrier density of 8 × 10 20 cm –3. Separate electron and hole relaxation times are observedmore » as a function of hot carrier energies. A first-order electron and hole decay of ~1 ps suggests a Shockley–Read–Hall recombination mechanism. Furthermore, the simultaneous observation of electrons and holes with extreme ultraviolet transient absorption spectroscopy paves the way for investigating few- to sub-femtosecond dynamics of both holes and electrons in complex semiconductor materials and across junctions.« less

Evaluation of thermal control coatings for use on solar dynamic radiators in low Earth orbit

NASA Technical Reports Server (NTRS)

Dever, Joyce A.; Rodriguez, Elvin; Slemp, Wayne S.; Stoyack, Joseph E.

1991-01-01

Thermal control coatings with high thermal emittance and low solar absorptance are needed for Space Station Freedom (SSF) solar dynamic power module radiator (SDR) surfaces for efficient heat rejection. Additionally, these coatings must be durable to low earth orbital (LEO) environmental effects of atomic oxygen, ultraviolet radiation and deep thermal cycles which occur as a result of start-up and shut-down of the solar dynamic power system. Eleven candidate coatings were characterized for their solar absorptance and emittance before and after exposure to ultraviolet (UV) radiation (200 to 400 nm), vacuum UV (VUV) radiation (100 to 200 nm) and atomic oxygen. Results indicated that the most durable and best performing coatings were white paint thermal control coatings Z-93, zinc oxide pigment in potassium silicate binder, and YB-71, zinc orthotitanate pigment in potassium silicate binder. Optical micrographs of these materials exposed to the individual environmental effects of atomic oxygen and vacuum thermal cycling showed that no surface cracking occurred.

Direct and simultaneous observation of ultrafast electron and hole dynamics in germanium.

PubMed

Zürch, Michael; Chang, Hung-Tzu; Borja, Lauren J; Kraus, Peter M; Cushing, Scott K; Gandman, Andrey; Kaplan, Christopher J; Oh, Myoung Hwan; Prell, James S; Prendergast, David; Pemmaraju, Chaitanya D; Neumark, Daniel M; Leone, Stephen R

2017-06-01

Understanding excited carrier dynamics in semiconductors is crucial for the development of photovoltaics and efficient photonic devices. However, overlapping spectral features in optical pump-probe spectroscopy often render assignments of separate electron and hole carrier dynamics ambiguous. Here, ultrafast electron and hole dynamics in germanium nanocrystalline thin films are directly and simultaneously observed by ultrafast transient absorption spectroscopy in the extreme ultraviolet at the germanium M 4,5 edge. We decompose the spectra into contributions of electronic state blocking and photo-induced band shifts at a carrier density of 8 × 10 20  cm -3 . Separate electron and hole relaxation times are observed as a function of hot carrier energies. A first-order electron and hole decay of ∼1 ps suggests a Shockley-Read-Hall recombination mechanism. The simultaneous observation of electrons and holes with extreme ultraviolet transient absorption spectroscopy paves the way for investigating few- to sub-femtosecond dynamics of both holes and electrons in complex semiconductor materials and across junctions.

Direct and simultaneous observation of ultrafast electron and hole dynamics in germanium

PubMed Central

Zürch, Michael; Chang, Hung-Tzu; Borja, Lauren J.; Kraus, Peter M.; Cushing, Scott K.; Gandman, Andrey; Kaplan, Christopher J.; Oh, Myoung Hwan; Prell, James S.; Prendergast, David; Pemmaraju, Chaitanya D.; Neumark, Daniel M.; Leone, Stephen R.

2017-01-01

Understanding excited carrier dynamics in semiconductors is crucial for the development of photovoltaics and efficient photonic devices. However, overlapping spectral features in optical pump-probe spectroscopy often render assignments of separate electron and hole carrier dynamics ambiguous. Here, ultrafast electron and hole dynamics in germanium nanocrystalline thin films are directly and simultaneously observed by ultrafast transient absorption spectroscopy in the extreme ultraviolet at the germanium M4,5 edge. We decompose the spectra into contributions of electronic state blocking and photo-induced band shifts at a carrier density of 8 × 1020 cm−3. Separate electron and hole relaxation times are observed as a function of hot carrier energies. A first-order electron and hole decay of ∼1 ps suggests a Shockley–Read–Hall recombination mechanism. The simultaneous observation of electrons and holes with extreme ultraviolet transient absorption spectroscopy paves the way for investigating few- to sub-femtosecond dynamics of both holes and electrons in complex semiconductor materials and across junctions. PMID:28569752

New solid state lasers from the ultraviolet to the mid-infrared

DOE Office of Scientific and Technical Information (OSTI.GOV)

Payne, S.A.; Krupke, W.F.; Beach, R.J.

The authors discuss three new laser materials that offer improved access to the ultraviolet, near infrared and mid-infrared spectral regions. In order for each of these materials to have been identified, a particular hurdle needed to be overcome with respect to the fundamental laser physics impacting the material. In the case of the 280-320nm Ce:LiSAF laser, the main issue is the need to reduce the loss associated with excited state absorption, while for 1047nm Yb:S-FAP it is the ground state absorption at the laser wavelength that must be minimized. Cr:ZnSe has been down-selected from a number of potential candidates whichmore » could lase in the 2200-3000nm region, in order to mitigate the detrimental impact of nonradiative decay. In all three cases the authors discuss how appropriate consideration of fundamental concerns has led to the identification and understanding of the new laser system.« less

The BUSS spectrum of Beta Lyrae. [Balloon-borne Ultraviolet Stellar Spectrograph

NASA Technical Reports Server (NTRS)

Hack, M.; Sahade, J.; De Jager, C.; Kondo, Y.

1983-01-01

The spectrum of Beta Lyrae from about 1975 to 3010 A taken with the Balloon-borne ultraviolet Stellar Spectrograph experiment in May 1976 at phase 0.61 P is analyzed. Results show the presence of N II semi-forbidden emission and provide evidence for about the same location, in the outer envelope of the system, of the layers responsible for the resonance Mg II doublet emissions and for the "narrow" H-alpha emission. In addition, three sets of absorption lines, P Cygni profiles of Fe III and broad Beals Type III emissions of Mg II, are found to be present.

The intriguing near-ultraviolet photochemistry of H 2Te

NASA Astrophysics Data System (ADS)

Underwood, J.; Chastaing, D.; Lee, S.; Boothe, P.; Flood, T. C.; Wittig, C.

2002-08-01

The ultraviolet absorption spectrum of H 2Te has a long wavelength tail that extends to 400 nm. Photodissociation at 355 nm yields TeH( 2Π 1/2) selectively relative to the 2Π 3/2 ground state; the transition moments for these channels lie in, and perpendicular to, the molecular plane, respectively. Vibrational structure in the region 380-400 nm is consistent with a shallow well in the adiabat leading to 2Π 1/2, akin to the one in HI leading to I( 2P 1/2). These effects have no counterparts with the light Group 6A dihydrides.

Effects of atomic oxygen and ultraviolet radiation on candidate elastomeric materials for long duration missions. Test series no.1

NASA Technical Reports Server (NTRS)

Linton, R. C.; Finckenor, M. M.; Kamenetzky, R. R.; Gray, P.

1993-01-01

Research was conducted at MSFC on the behavior of elastomeric materials after exposure to simulated space environment. Silicone S383 and Viton V747 samples were exposed to thermal vacuum, ultraviolet radiation, and atomic oxygen and then evaluated for changes in material properties. Characterization of the elastomeric materials included weight, hardness, optical inspection under normal and black light, spectrofluorescence, solar absorptance and emittance, Fourier transform infrared spectroscopy, and permeability. These results indicate a degree of sensitivity to exposure and provided some evidence of UV and atomic oxygen synergism.

Complete erasing of ghost images on computed radiography plates and role of deeply trapped electrons

NASA Astrophysics Data System (ADS)

Ohuchi-Yoshida, Hiroko; Kondo, Yasuhiro

2011-12-01

Computed radiography (CR) plates made of europium-doped Ba(Sr)FBr(I) were simultaneously exposed to filtered ultraviolet light and visible light in order to erase ghost images, i.e., latent image that is unerasable with visible light (LIunVL) and reappearing one, which are particularly observed in plates irradiated with a high dose and/or cumulatively over-irradiated. CR samples showing LIunVLs were prepared by irradiating three different types of CR plates (Agfa ADC MD10, Kodak Directview Mammo EHRM2, and Fuji ST-VI) with 50 kV X-ray beams in the dose range 8.1 mGy-8.0 Gy. After the sixth round of simultaneous 6 h exposures to filtered ultraviolet light and visible light, all the LIunVLs in the three types of CR plates were erased to the same level as in an unirradiated plate and no latent images reappeared after storage at 0 °C for 14 days. With conventional exposure to visible light, LIunVLs consistently remained in all types of CR plates irradiated with higher doses of X-rays and latent images reappeared in the Agfa M10 plates after storage at 0 °C. Electrons trapped in deep centers cause LIunVLs and they can be erased by simultaneous exposures to filtered ultraviolet light and visible light. To study electrons in deep centers, the absorption spectra were examined in all types of irradiated CR plates by using polychromatic ultraviolet light from a deep-ultraviolet lamp. It was found that deep centers showed a dominant peak in the absorption spectra at around 324 nm for the Agfa M10 and Kodak EHRM2 plates, and at around 320 nm for the Fuji ST-VI plate, in each case followed by a few small peaks. The peak heights were dose-dependent for all types of CR samples, suggesting that the number of electrons trapped in deep centers increases with the irradiation dose.

Sulfur and Sulfuric Acid Microphysics in the Venus Atmosphere: Implications for the Unknown UV Absorber

NASA Astrophysics Data System (ADS)

Gao, P.; Carlson, R. W.; Robinson, T. D.; Crisp, D.; Lyons, J. R.; Yung, Y. L.

2016-12-01

A mystery that has continued to plague our sister planet, Venus, for nearly a century is the nature of the brightness contrasts observed crisscrossing its disk in near-ultraviolet wavelength images. These contrasts - specifically the dark regions - have been attributed to the actions of an unknown UV absorber, knowing the identity of which is integral to understanding the Venus atmosphere due to the high rates of mesospheric heating attributed to the absorption of solar UV. One possible candidate for the UV absorber is polysulfur, which form from polymerization of elemental sulfur arising from SO2 photolysis at the Venus cloud tops under low O2 conditions. In this work we investigate the microphysics of condensed polysulfur and its interaction with the sulfuric acid clouds. We consider the "gumdrop model", where sulfur is allowed to condense onto sulfuric acid cloud particles. We explore the possibility that S2 vapor may condense faster than its loss to gas phase reactions that produce higher allotropes, leading to solid state polymerization to S8. This process may explain the ephemeral and variable nature of the UV absorption.

Combined toxicity of silica nanoparticles and methylmercury on cardiovascular system in zebrafish (Danio rerio) embryos.

PubMed

Duan, Junchao; Hu, Hejing; Li, Qiuling; Jiang, Lizhen; Zou, Yang; Wang, Yapei; Sun, Zhiwei

2016-06-01

This study was to investigate the combined toxicity of silica nanoparticles (SiNPs) and methylmercury (MeHg) on cardiovascular system in zebrafish (Danio rerio) embryos. Ultraviolet absorption analysis showed that the co-exposure system had high absorption and stability. The dosages used in this study were based on the NOAEL level. Zebrafish embryos exposed to the co-exposure of SiNPs and MeHg did not show any cardiovascular malformation or atrioventricular block, but had an inhibition effect on bradycardia. Using o-Dianisidine for erythrocyte staining, the cardiac output of zebrafish embryos was decreased gradually in SiNPs, MeHg, co-exposure groups, respectively. Co-exposure of SiNPs and MeHg enhanced the vascular endothelial damage in Tg(fli-1:EGFP) transgenic zebrafish line. Moreover, the co-exposure significantly activated the oxidative stress and inflammatory response in neutrophils-specific Tg(mpo:GFP) transgenic zebrafish line. This study suggested that the combined toxic effects of SiNPs and MeHg on cardiovascular system had more severe toxicity than the single exposure alone. Copyright © 2016 Elsevier B.V. All rights reserved.

Catalog of far-ultraviolet objective-prism spectrophotometry: Skylab experiment S-019, ultraviolet steller astronomy

NASA Technical Reports Server (NTRS)

Henize, K. G.; Wray, J. D.; Parsons, S. B.; Benedict, G. F.

1979-01-01

Ultraviolet stellar spectra in the wavelength region from 1300 to 5000 A (130 to 500) were photographed during the three manned Skylab missions using a 15 cm aperture objective-prism telescope. The prismatic dispersion varied from 58 A mm/1 at 1400 A to 1600 A mm/1 at 3000 A. Approximately 1000 spectra representing 500 stars were measured and reduced to observed fluxes. About 100 stars show absorption lines of Si IV, C IV, or C II. Numerous line features are also recorded in supergiant stars, shell stars, A and F stars, and Wolf-Rayet stars. Most of the stars in the catalog are of spectral class B, with a number of O and A type stars and a sampling of WC, WN, F and C type stars. Spectrophotometric results are tabulated for these 500 stars.

Energy deposition in ultrathin extreme ultraviolet resist films: extreme ultraviolet photons and keV electrons

NASA Astrophysics Data System (ADS)

Kyser, David F.; Eib, Nicholas K.; Ritchie, Nicholas W. M.

2016-07-01

The absorbed energy density (eV/cm3) deposited by extreme ultraviolet (EUV) photons and electron beam (EB) high-keV electrons is proposed as a metric for characterizing the sensitivity of EUV resist films. Simulations of energy deposition are used to calculate the energy density as a function of the incident aerial flux (EUV: mJ/cm2, EB: μC/cm2). Monte Carlo calculations for electron exposure are utilized, and a Lambert-Beer model for EUV absorption. The ratio of electron flux to photon flux which results in equivalent energy density is calculated for a typical organic chemically amplified resist film and a typical inorganic metal-oxide film. This ratio can be used to screen EUV resist materials with EB measurements and accelerate advances in EUV resist systems.

Intercalation of anionic organic ultraviolet ray absorbers into layered zinc hydroxide nitrate.

PubMed

Cursino, Ana Cristina Trindade; Gardolinski, José Eduardo Ferreira da Costa; Wypych, Fernando

2010-07-01

Layered zinc hydroxide nitrate (ZHN) was synthesized and nitrate ions were topotactically exchanged with three different anionic species of commercial organic ultraviolet (UV) ray absorbers: 2-mercaptobenzoic acid, 2-aminobenzoic acid, and 4-aminobenzoic acid. The exchange reactions were confirmed by X-ray powder diffraction (XRPD), Fourier transform infrared spectroscopy (FTIR), ultraviolet visible (UV-Vis) spectroscopy, and thermal analysis (thermogravimetry, TGA, and differential thermal analysis, DTA). In all the anionic exchanged products, evidence of grafting of the organic species onto the inorganic matrix was obtained. In general, after intercalation/grafting, the UV absorption ability was improved in relation to the use of the parent organic material, showing that layered hydroxide salts (LHS) can be good alternative matrixes for the immobilization of organic species with UV-blocking properties in cosmetic products. Copyright 2010 Elsevier Inc. All rights reserved.

Ultrafast carrier dynamics of titanic acid nanotubes investigated by transient absorption spectroscopy.

PubMed

Wang, Li; Zhao, Hui; Pan, Lin Yun; Weng, Yu Xiang; Nakato, Yoshihiro; Tamai, Naoto

2010-12-01

Carrier dynamics of titanic acid nanotubes (phase of H2Ti2O5.H2O) deposited on a quartz plate was examined by visible/near-IR transient absorption spectroscopy with an ultraviolet excitation. The carrier dynamics of titanic acid nanotubes follows the fast trapping process which attributed to the intrinsic tubular structure, the relaxation of shallow trapped carriers and the recombination as a second-order kinetic process. Transient absorption of titanic acid nanotubes was dominated by the absorption of surface-trapped holes in visible region around 500 nm, which was proved by the faster decay dynamics in the presence of polyvinyl alcohol as a hole-scavenger. However, the slow relaxation of free carriers was much more pronounced in the TiO2 single crystals, as compared with the transient absorption spectra of titanic acid nanotubes under the similar excitation.

Band gap of corundumlike α -Ga2O3 determined by absorption and ellipsometry

NASA Astrophysics Data System (ADS)

Segura, A.; Artús, L.; Cuscó, R.; Goldhahn, R.; Feneberg, M.

2017-07-01

The electronic structure near the band gap of the corundumlike α phase of Ga2O3 has been investigated by means of optical absorption and spectroscopic ellipsometry measurements in the ultraviolet (UV) range (400-190 nm). The absorption coefficient in the UV region and the imaginary part of the dielectric function exhibit two prominent absorption thresholds with wide but well-defined structures at 5.6 and 6.3 eV which have been ascribed to allowed direct transitions from crystal-field split valence bands to the conduction band. Excitonic effects with large Gaussian broadening are taken into account through the Elliott-Toyozawa model, which yields an exciton binding energy of 110 meV and direct band gaps of 5.61 and 6.44 eV. The large broadening of the absorption onset is related to the slightly indirect character of the material.

Interpretation of the prominence differential emissions measure for 3 geometries

NASA Technical Reports Server (NTRS)

Schmahl, E. J.; Orrall, F. Q.

1986-01-01

Researchers have used prominence extreme ultraviolet line intensities observed from Skylab to derive the differential emission measure Q(T) in the prominence-corona (PC) interface from 3 x 10,000 to 3 times 1 million K, including the effects of Lyman Continuum absorption. Using lines both shortward and longward of the Lyman limit, researchers have estimated the importance of absorption as function of temperature. The magnitude of the absorption, as well as its rate of increase as a function of temperature, place limits on the thread scales and the character of the interfilar medium. Researchers have calculated models based on three assumed geometries: (1) threads with hot sheaths and cool cores; (2) isothermal threads; and (3) threads with longitudinal temperature gradients along the magnetic field. Comparison of the absorption computed from these models with the observed absorption in prominences shows that none of the geometries is totally satisfactory.

Observations of absorption lines from highly ionized atoms. [of interstellar medium

NASA Technical Reports Server (NTRS)

Jenkins, Edward B.

1987-01-01

In the ultraviolet spectra of hot stars, absorption lines can be seen from highly ionized species in the interstellar medium. Observations of these features which have been very influential in revising the perception of the medium's various physical states, are discussed. The pervasiveness of O 6 absorption lines, coupled with complementary observations of a diffuse background in soft X-rays and EUV radiation, shows that there is an extensive network of low density gas (n approx. few x 0.001/cu cm) existing at coronal temperatures log T = 5.3 or 6.3. Shocks created by supernova explosions or mass loss from early-type stars can propagate freely through space and eventually transfer a large amount of energy to the medium. To create the coronal temperatures, the shocks must have velocities in excess of 150 km/sec; shocks at somewhat lower velocity (v = 100 km/sec) can be directly observed in the lines of Si3. Observations of other lines in the ultraviolet, such as Si 4V and C 5, may highlight the widespread presence of energetic UV radiation from very hot, dwarf stars. More advanced techniques in visible and X-ray astronomical spectroscopy may open up for inspection selected lines from atoms in much higher stages of ionization.

Observations of Absorption Lines from Highly Ionized Atoms

NASA Technical Reports Server (NTRS)

Jenkins, E. B.

1984-01-01

In the ultraviolet spectra of hot stars, absorption lines can be seen from highly ionized species in the interstellar medium. Observations of these features which have been very influential in revising the perception of the medium's various physical states, are discussed. The pervasiveness of O 6 absorption lines, coupled with complementary observations of a diffuse background in soft X-rays and EUV radiation, shows that there is an extensive network of low density gas (n approx. fewX 0.001/cucm) existing at coronal temperatures, 5.3 or = log T or = 6.3. Shocks created by supernova explosions or mass loss from early-type stars can propagate freely through space and eventually transfer a large amount of energy to the medium. To create the coronal temperatures, the shocks must have velocities in excess of 150 km/sec; shocks at somewhat lower velocity 9v or = 100 km/sec) can be directly observed in the lines of Si3. Observations of other lines in the ultraviolet, such as Si 4V and C 5, may highlight the widespread presence of energetic uv radiation from very hot, dward stars. More advanced techniques in visible and X-ray astronomical spectroscopy may open up for inspection selected lines from atoms in much higher stages of ionization.

FT-IR spectroscopic studies of polycyclic aromatic hydrocarbons

NASA Technical Reports Server (NTRS)

Salisbury, D. W.; Allen, J. E., Jr.; Donn, B.; Moore, W. J.; Khanna, R. K.

1990-01-01

Proper assessment of the hypothesis which correlates polycyclic aromatic hydrocarbons (PAHs) with the unidentified infrared emission bands requires additional experimental laboratory data. In order to address this need, thermal infrared emission studies were performed on a subset of PAHs suggested to be of astrophysical importance. It was proposed that infrared emission from interstellar PAHs occurs following absorption of an ultraviolet photon. Since energy transfer to the ground electronic state can be rapid for a species in which intersystem crossing is negligible, the emission spectrum may be viewed as resulting from an equilibrium vibrational temperature (Leger and d'Hendecourt, 1987). This has been the basis for using infrared absorption spectra to calculate the corresponding emission spectra at various temperatures. These calculations were made using room temperature infrared absorption coefficients instead of those at the temperature of interest because of the latter's unavailability. The present studies are designed to address the differences between the calculated and experimental thermal emission spectra and to provide information which will be useful in future ultraviolet induced infrared fluorescence studies. The emission spectra have been obtained for temperatures up to 825K using an emission cell designed to mount against an external port of an FT-IR spectrometer. These spectra provide information concerning relative band intensities and peak positions which is unavailable from previous calculations.

UV-Assisted Photochemical Synthesis of Reduced Graphene Oxide/ZnO Nanowires Composite for Photoresponse Enhancement in UV Photodetectors

PubMed Central

Zhou, Peng; Wang, Na; Ma, Yang

2018-01-01

The weak photon absorption and high recombination rate of electron-hole pairs in disordered zinc oxide nanowires (ZNWs) limit its application in UV photodetection. This limitation can be overcome by introducing graphene sheets to the ZNWs. Herein we report a high-performance photodetector based on one-dimensional (1D) wide band-gap semiconductor disordered ZNWs composited with reduced graphene oxide (RGO) for ultraviolet (UV) photoresponse enhancement. The RGO/ZNWs composites have been successfully synthetized through UV-assisted photochemical reduction of GO in ZNWs suspension. The material characterizations in morphology, Raman scattering, and Ultraviolet-visible light absorption verified the formation of graphene sheets attached in ZNWs network and the enhancement of UV absorption due to the introduction of graphene. In comparison with photodetectors based on pure ZNWs, the photodetectors based on RGO/ZNWs composite exhibit enhanced photoresponse with photocurrent density of 5.87 mA·cm−2, on/off current ratio of 3.01 × 104, and responsivity of 1.83 A·W−1 when a UV irradiation of 3.26 mW·cm−2 and 1.0 V bias were used. Theory analysis is also presented to get insight into the inherent mechanisms of separation and transportation of photo-excited carriers in RGO/ZNWs composite. PMID:29303994

UV-Assisted Photochemical Synthesis of Reduced Graphene Oxide/ZnO Nanowires Composite for Photoresponse Enhancement in UV Photodetectors.

PubMed

Chen, Changsong; Zhou, Peng; Wang, Na; Ma, Yang; San, Haisheng

2018-01-05

The weak photon absorption and high recombination rate of electron-hole pairs in disordered zinc oxide nanowires (ZNWs) limit its application in UV photodetection. This limitation can be overcome by introducing graphene sheets to the ZNWs. Herein we report a high-performance photodetector based on one-dimensional (1D) wide band-gap semiconductor disordered ZNWs composited with reduced graphene oxide (RGO) for ultraviolet (UV) photoresponse enhancement. The RGO/ZNWs composites have been successfully synthetized through UV-assisted photochemical reduction of GO in ZNWs suspension. The material characterizations in morphology, Raman scattering, and Ultraviolet-visible light absorption verified the formation of graphene sheets attached in ZNWs network and the enhancement of UV absorption due to the introduction of graphene. In comparison with photodetectors based on pure ZNWs, the photodetectors based on RGO/ZNWs composite exhibit enhanced photoresponse with photocurrent density of 5.87 mA·cm -2 , on/off current ratio of 3.01 × 10⁴, and responsivity of 1.83 A·W -1 when a UV irradiation of 3.26 mW·cm -2 and 1.0 V bias were used. Theory analysis is also presented to get insight into the inherent mechanisms of separation and transportation of photo-excited carriers in RGO/ZNWs composite.

Chemical Properties of Brown Carbon Aerosol Generated at the Missoula Fire Sciences Laboratory

NASA Astrophysics Data System (ADS)

Washenfelder, R. A.; Womack, C.; Franchin, A.; Middlebrook, A. M.; Wagner, N.; Manfred, K.

2017-12-01

Aerosol scattering and absorption are still among the largest uncertainties in quantifying radiative forcing. Biomass burning is a major source of light-absorbing carbonaceous aerosol in the United States. These aerosol are generally classified into two categories: black carbon (graphitic-like aerosol that absorbs broadly across the ultraviolet and visible spectral regions) and brown carbon (organic aerosol that absorbs strongly in the ultraviolet and near-visible spectral regions). The composition, volatility, and chemical aging of brown carbon are poorly known, but are important to understanding its radiative effects. We deployed three novel instruments to the Missoula Fire Sciences Laboratory in 2016 to measure brown carbon absorption: a photoacoustic spectrometer, broadband cavity enhanced spectrometer, and particle-into-liquid sampler coupled to a liquid waveguide capillary cell. The instruments sampled from a shared inlet with well-characterized dilution and thermal denuding. We sampled smoke from 32 controlled burns of fuels relevant to western U.S. wildfires. We use these measurements to determine the volatility of water-soluble brown carbon, and compare this to the volatility of water-soluble organic aerosol and total organic aerosol. We further examine the wavelength-dependence of the water-soluble brown carbon absorption as a function of denuder temperature. Together this gives new information about the solubility, volatility, and chemical composition of brown carbon.

Indirect ultraviolet detection of alkaline earth metal ions using an imidazolium ionic liquid as an ultraviolet absorption reagent in ion chromatography.

PubMed

Liu, Yong-Qiang; Yu, Hong

2017-04-01

A convenient and versatile method was developed for the separation and detection of alkaline earth metal ions by ion chromatography with indirect UV detection. The chromatographic separation of Mg 2+ , Ca 2+ , and Sr 2+ was performed on a carboxylic acid base cation exchange column using imidazolium ionic liquid/acid as the mobile phase, in which the imidazolium ionic liquid acted as an UV-absorption reagent. The effects of imidazolium ionic liquids, detection wavelength, acids in the mobile phase, and column temperature on the retention of Mg 2+ , Ca 2+ , and Sr 2+ were investigated. The main factors influencing the separation and detection were the background UV absorption reagent and the concentration of hydrogen ion in ion chromatography with indirect UV detection. The successful separation and detection of Mg 2+ , Ca 2+ , and Sr 2+ within 14 min were achieved using the selected chromatographic conditions, and the detection limits (S/N = 3) were 0.06, 0.12, and 0.23 mg/L, respectively. A new separation and detection method of alkaline earth metal ions by ion chromatography with indirect UV detection was developed, and the application range of ionic liquids was expanded. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Observations of the interstellar medium with IUE

NASA Technical Reports Server (NTRS)

Jenkins, E. B.

1981-01-01

Limitations of the International Ultraviolet Explorer (IUE) are discussed, as well as improved powers of research in these areas: (1) Si and C IV doublet absorptions in the high dispersion stellar spectra of distant stars; (2) observation of spectra outside the galactic plans; (3) high velocity gas.

Testing of Cerex Open-Path Ultraviolet Differential Optical Absorption Spectroscopy Systems for Fenceline Monitoring Applications

EPA Science Inventory

Development of cost-effective, time-resolved fenceline measurement methods that facilitate improved emissions mitigation strategies is of growing interest to both industry and regulators. Ground-based optical remote sensing (ORS) is a well-known class of technical approaches use...

Testing of Cerex Open-Path Ultraviolet Differential Optical Absorption Spectroscopy System for Fenceline Monitoring Applications

EPA Science Inventory

Development of cost-effective, time-resolved fenceline measurement methods that facilitate improved emissions mitigation strategies is of growing interest to both industry and regulators. Ground-based optical remote sensing (ORS) is a well-known class of technical approaches use...

Testing of Cerex Open Path Ultraviolet Differential Optical Absorption Spectroscopy Systems for Fenceline Monitoring Applications

EPA Science Inventory

Industrial facilities, energy production, and refining operations can be significant sources of gas-phase air pollutants. Some industrial emissions originate from fugitive sources (leaks) or process malfunctions and can be mitigated if identified. In recent amendments to the Nati...

Broadband cavity-enhanced absorption spectroscopy in the ultraviolet spectral region for measurements of nitrogen dioxide and formaldehyde

NASA Astrophysics Data System (ADS)

Washenfelder, R. A.; Attwood, A. R.; Flores, J. M.; Zarzana, K. J.; Rudich, Y.; Brown, S. S.

2016-01-01

Formaldehyde (CH2O) is the most abundant aldehyde in the atmosphere, and it strongly affects photochemistry through its photolysis. We describe simultaneous measurements of CH2O and nitrogen dioxide (NO2) using broadband cavity-enhanced absorption spectroscopy in the ultraviolet spectral region. The light source consists of a continuous-wave diode laser focused into a Xenon bulb to produce a plasma that emits high-intensity, broadband light. The plasma discharge is optically filtered and coupled into a 1 m optical cavity. The reflectivity of the cavity mirrors is 0.99930 ± 0.00003 (1- reflectivity = 700 ppm loss) at 338 nm, as determined from the known Rayleigh scattering of He and zero air. This mirror reflectivity corresponds to an effective path length of 1.43 km within the 1 m cell. We measure the cavity output over the 315-350 nm spectral region using a grating monochromator and charge-coupled device array detector. We use published reference spectra with spectral fitting software to simultaneously retrieve CH2O and NO2 concentrations. Independent measurements of NO2 standard additions by broadband cavity-enhanced absorption spectroscopy and cavity ring-down spectroscopy agree within 2 % (slope for linear fit = 1.02 ± 0.03 with r2 = 0.998). Standard additions of CH2O measured by broadband cavity-enhanced absorption spectroscopy and calculated based on flow dilution are also well correlated, with r2 = 0.9998. During constant mixed additions of NO2 and CH2O, the 30 s measurement precisions (1σ) of the current configuration were 140 and 210 pptv, respectively. The current 1 min detection limit for extinction measurements at 315-350 nm provides sufficient sensitivity for measurement of trace gases in laboratory experiments and ground-based field experiments. Additionally, the instrument provides highly accurate, spectroscopically based trace gas detection that may complement higher precision techniques based on non-absolute detection methods. In addition to trace gases, this approach will be appropriate for measurements of aerosol extinction in ambient air, and this spectral region is important for characterizing the strong ultraviolet absorption by brown carbon aerosol.